French Chocolate Flan Pâtissier

Chocolate Pate Sucreé Crust
1 In the bowl of a stand mixer fitted with the paddle attachment, cream the softened butter and sugar together until smooth.
2 Using a mixing bowl, whisk together the flour, almond meal, cocoa powder, and salt.
3 On low speed mix in 1/2 of the beaten egg and 1/2 of the flour mixture. Mix until combined. Scrape the bottom and sides of the bowl with a spatula. Repeat with the remaining ingredients to form a soft cookie dough texture.
4 Scoop any crumbs stuck to the bottom of the bowl and pack the dough together by hand.
5 Divide the dough into two equal halves. Pack the dough into flat discs with your hands.
6 Wrap the dough in plastic film and rest in the fridge for a minimum of 1 hour or better overnight.
Line the Tart Ring
42 I'm using a 20cm (8-inch) smooth pastry ring for this Flan. You can also use an 8-inch springform pan with a removeable bottom. Measure the strips to fit the inside circumference of the mold you're using and a bottom disc of dough slightly smaller than the diameter of the ring or pan. Overlaps are just fine and help seal the dough together.
8 Roll out one half of the dough between two layers of parchment paper to 1/8-1/4 inch (3-5mm). Take a ruler or pastry cutter and cut two strips of dough  about 13-inches (33 cm) long and slightly wider than the thickness of the pastry ring. These will be used to line the inside of the pastry ring.
9 Place the strips in the fridge or freezer on parchment paper to chill while rolling out the second half.
10 Roll out the second half of dough between parchment paper to the same thickness and cut a disc in the 7 ¾ inches (19.5 cm) in diameter. It needs to be slightly smaller than the ring. Chill the disc if it becomes soft.
11 Place your pastry ring on a perforated silicone mat and perforated pan. Or on a baking sheet lined with parchment paper. 
12 Line the inside of the ring with the the two strips of pastry. Pressing the dough flush with the ring. Seal any overlaps with your fingers. 
13 Lower the pastry disc into the circle, flush with the pan. Gently use your fingertips to press the sides and bottom together. If you have any cracks or openings, seal with spare dough. 
14 Place the pan with the tart ring in the freezer for at least one hour to freeze completely. 
Optional - Partially Bake Crust
41 For a crispier tart crust, partially bake the empty frozen shell first. 
40 Line the frozen crust with parchment paper and fill with pie weights or dried beans. Bake at 350°F (180°C) conventional oven for 15 minutes. Remove the weights and let cool before adding the chocolate cream.
Chocolate Pastry Cream
16 Set up your workstation so everything is laid out and next to the stove to make things easier and less stressful for you. Place an empty bowl on the counter close by lined with a metal sieve. .
17 Stir together the milk, cream, half of the sugar, vanilla, and espresso powder in a large saucepan on medium heat.
18 Meanwhile in a large mixing bowl hand whisk together the eggs, yolks, and remaining half of the sugar into a thick liquid. Use a little elbow grease, whisk in the sifted cornstarch a little at a time to avoid lumps. Whisk until the cornstarch is completely dissolved into a smooth mixture.
19 Once the milk and cream reach a simmer, slowly pour half into the eggs while continuously whisking to temper the mixture.
20 Now pour the egg mixture back into the saucepan while stirring on medium heat.
21 Continuously whisk as the custard starts to thicken. This will happen pretty quickly in just a minute or two. It's important to keep whisking to prevent a lumpy custard.
22 As it thickens it will come to a boil. You'll notice it's ready when you stop whisking and the mixture kind of burps up a few air pockets. Whisk vigorously for a smooth glossy pastry cream and then remove from the heat.
23 Transfer the pastry cream to a heat proof bowl. Add in the chopped chocolate and stir with a spatula until the chocolate is entirely melted. 
25 Take a handheld immersion blender and blend the mixture into a silky consistency. This is optional, but really helps create a smooth pastry cream with the addition of chocolate. 
24 Place a sheet of plastic film directly on the surface and refrigerate until cool. 
Fill and Bake
28 Preheat the oven to 400℉ (200℃) conventional setting or 375℉ (180℃) fan setting. 
27 Remove the cooled pastry cream from the fridge and give it a good hand whisk to smooth it out. 
29 Trim the excess pastry from the top of the pastry ring using a small knife, cutting away from yourself. 
30 Pour the chocolate pastry cream into the frozen crust and level with an offset spatula. 
31 Place the pan on the middle oven rack and bake for 10 minutes. 
32 Lower the oven temperature to 350℉ (180℃) conventional setting or 325℉ (160℃) fan setting. Bake for an additional 45 minutes.
33 The center of the flan will puff up towards the end of baking, this is normal. The top layer will also become matte and may darken in some areas. When the pan is jiggled slightly the flan should still have a nice wobble. 
34 Place the pan on a wire rack and cool completely. (about 3 hours) (NEVER unmold while it's still hot, or it will collapse).
35 Keep the flan in the ring and refrigerate for at least 4 hours. I prefer to chill mine overnight.
Unmold and Serve
36 Once properly chilled, run an offset spatula between the crust and the ring. Lift the ring from the flan. Carefully transfer to a serving dish.
38 Warm either simple syrup or apricot jam in a small bowl. Using a pastry brush, gently paint thin coating across the top of the flan for a shiny top. Slice and serve.