Black & White Tartelettes

My husband and I were on a double mission:

1. For my husband: Find a youth-size Red Sox baseball cap. 
2. For me: Find hazelnuts for the dessert I had in mind. 

Surprisingly, we were able to find both on Newbury street! I was so ready to give up on the hazelnuts - after checking out a bunch of stores, I was almost convinced that walnuts, pecans and cashews are the only types of nuts in the world. But this mini-market (or, micro-market) on Newbury street eventually came to the rescue - it even had peeled and unpeeled hazelnuts to choose from! I took the peeled ones, of course... peeling is a pain!...

This dessert is basically my attempt to re-create the flavor combination that the amazing Black & White dessert from Babbo Pizzeria has - Chocolate, Crème fraîche, Hazelnuts and Caramel. 
Well - I decided that Greek yogurt is close enough to Crème fraîche, and that dulce de leche is close enough to Caramel (it isn't, really... but after a couple of Caramel-related disasters that I had in the kitchen, I stuck to the safer choice; plus, I already had a jar of dulce de leche that was just begging me to use it... how could I refuse?...). 

Note that I am not using special tartelette pans (I don't have any... yet...) - instead, I'm using a regular cupcakes/muffin pan. 

The tartelettes crust in this recipe is based on a chocolate "porcupine" recipe by Micky Shemo.
The inspiration for the nutty-bottom-layer is from a Pistachio-Chocolate Tart recipe by Chen Shukrun.
The chocolate layer is based on a Grappa-chocolate Tart recipe published on ynet.
The yogurt layer is based on a Cheese-Chocolate Spiral-Cake recipe by Carine Goren.

Black & White Tartelettes
Yields: 12 Tartelettes

WHAT:
for the crust: 

• 70 grams sugar
• 1 stick unsalted butter, cold, cubed
• 1 egg
• 210 grams (1 1/2 cups) all-purpose flour
• 10 grams (1 tbsp) unsweetened cocoa powder
• 1/2 tsp baking powder
• [optional, if mixture is too dry] 1-2 tsp milk
• [optional, if mixture is too soft/wet] 1-2 tsp flour

for the nutty-bottom-layer:

• 100 grams peeled hazelnuts
• a pinch of salt
• 35 grams sugar
• 2 tbsp vegetable oil (not olive oil!)

for the milk chocolate layer:

• 170 grams (6 ounce) milk chocolate
• 1/2 stick unsalted butter
• 1 egg
• 15 grams corn starch
• 20 grams all purpose flour
• a pinch of salt

for the yogurt layer:

• 70 grams white chocolate
• 30 ml heavy cream
• 200 grams (1 small package) Greek Strained Yogurt
• 25 grams sugar
• 1 egg
• 1 tsp corn starch

for the dulce de leche frosting:

• 2 overloaded tbsp dulce de leche
• 1 cup heavy cream
• 1 tsp vanilla pudding mix (powder)

for decoration (optional):

• peeled hazelnuts, coarsely-chopped. 

HOW:

• Crust: Sift flour, cocoa powder and baking powder into a large bowl.
• In a food processor or a mixer with a flat beater, mix together butter and sugar until well combined. 
• Add in egg and a quarter of the flour/cocoa mixture. Mix for a few seconds. 
• Add in the rest of the flour/cocoa mixture. Mix until a large dough-ball is formed, not beyond. 
• If mixture is too dry and not solidifying into a ball, add 1 or 2 tsp of milk, as needed. 
• If mixture is too soft/wet and not solidifying into a ball, add 1 or 2 tsp of flour, as needed. 
• Form the dough into a 1/2 inch thick disc shape. 
• Wrap the dough in plastic wrap, and refrigerate for 30 minutes (or more). 
• Pre-heat oven to 355 degrees (F). 
• Remove refrigerated dough from plastic wrap, and knead/mold a little with your hands, to warm it up a bit. 
• Using a rolling pin, flatten the dough to be ~3-4 mm thick on a generously-flour-dusted surface. 
• Using a 4-inch-diameter cookie/biscuit cutter or a similar tool with which you can cut round shapes (e.g. a small bowl), cut 12 "discs" out of the flattened dough. 
• [Leftover dough? Make some peanut-butter chocolate sandwich cookies!]
• Line a regular cupcake/muffin pan with the dough "discs" (no need to oil the pan or line it with paper liners), pressing each disc to the bottom and sides of each cupcake/muffin "cavity" to form the tartelettes' crusts. 
• Using a fork, puncture the bottom of each disc a couple of times (to prevent air-pockets). 
• Nutty bottom layer: In a food processor, finely grind the hazelnuts with salt and sugar. 
• Add in oil, and continue processing until well combined and mixture consistency resembles damp sand. 
• Put ~1 overloaded teaspoon of ground-nuts-mixture into each tartelette crust. 
• Using a small glass or another tool (or even a teaspoon), press the nuts-mixture firmly onto the crust bottom. 
• Wrap the pan tightly in plastic wrap or aluminum foil and freeze for ~10 minutes. 
• Remove pan from freezer, remove wrap. 
• Immediately transfer pan to the oven, bake for ~7 minutes.
• Take pan out of the oven, set aside in room temperature to cool down, until pre-bake assembly. Keep crusts in the pan. Crusts' bottoms might have risen a bit while being in the oven - they will "fall" back down while cooling. 
• Lower oven temperature to 300 degrees (F).
• Milk chocolate layer (prepare while pan is cooling down): Place milk chocolate and butter in a medium bowl. Heat in microwave or over a double boiler until chocolate and butter are melted. Mix together until well combined. Set aside to cool down a bit. 
• Beat egg (with a fork or a small whisk) in a small bowl for ~1 minute.
• Add egg into the cooled-down chocolate. Beat until egg is well combined - mixture should become very smooth and glossy. 
• Sift flour, corn starch and salt into the chocolate mixture. Beat together until well combined. 
• Yogurt layer: Place white chocolate and heavy cream in a small bowl. Heat in microwave or over a double boiler until chocolate is melted. Mix together until well combined. Set aside to cool down a bit. 
• In a medium bowl, mix together the Greek yogurt and the sugar until the sugar dissolves.
• Add in the egg and mix until well combined. 
• Add the white chocolate ganache to the yogurt mixture. Mix together until well combined. 
• Transfer a small amount (~1/3 cup) of the yogurt mixture to a clean small bowl. Add the corn starch to that bowl. Mix together until well combined. 
• Transfer the corn-starch-mixture back to the medium ball with the rest of the yogurt-mixture. Mix everything together until well combined. 
• Pre-bake assembly: After crusts have cooled down from their initial baking, fill each crust with the milk-chocolate mixture until ~1/2 full (I used a pasty bag with a large round metal tip). 
• Fill each tartelette crust with the yogurt mixture (on top of the milk-chocolate layer) until tartelette is completely full (the yogurt mixture is a bit more liquid-y, so using any vessel with a pouring tip such as a measuring glass should do the work). 
• Carefully transfer the pan to the oven. Bake tartelettes for 20-25 minutes. 
• Remove pan from the oven, let it sit in room temperature until completely cooled down, ~1 hour. 
• At this stage, it is recommended to transfer the tartelettes to the container that will be put in the fridge for the final cooling/setting.
  You can put each tartelette in a cupcake-paper-liner at this stage, if you'd like.
  In order to take the tartelettes out of the pan, use a very thin small knife or a small offset spatula (slide knife/spatula between the crust and the pan and gently lift the tartelette on one side; take the tartelette out of the pan with your other hand). 
• Dulce de leche frosting: Whip together all frosting ingredients on high speed, until firm. 
• Using a pastry bag with a star tip, frost each tartelette with the frosting. 
• [Optional] Decorate each tartelette with some coarsely chopped hazelnuts. 
• Refrigerate the tartelettes in an air-tight container for at least 4 hours, preferably overnight.
• Enjoy!

Leftovers? Keep the tartelettes in an air-tight container in the fridge. 

The tartelettes are at their best on the first two days (after the overnight cooling), afterwards the crust may become softer. 

I recommend to consume within 4-5 days.