Chocolate Pastry Cream

Optional for more stable pastry cream:

2 teaspoons powdered gelatin

2 tablespoons water

2 1/4 cups (540 grams) whole milk
1/2 cup (100 grams) brown sugar (or can use white sugar)
2 egg yolks from large eggs
2 large eggs (or substitute 2 egg yolks for slightly thicker version)
2 1/2 tablespoons (25 grams) cornstarch 
2 tablespoons (18 grams) dutch-processed cocoa powder
2 teaspoons vanilla extract 
1/4 teaspoon sea salt
170 grams bittersweet chocolate, chopped
2 tablespoons (30 grams) unsalted butter, softened

If using gelatin: Place the water in a small bowl and sprinkle the gelatin over the water. Mix gently and allow the gelatin to bloom.

Put the milk in a saucepan. Heat over medium high heat until steaming. It's not necessary to boil the milk but it's okay if it does boil gently.

While the milk is heating, place the sugar, eggs, cornstarch, cocoa powder, vanilla, and salt in a bowl. Whisk until you have a thick, smooth mixture. Place the bowl on a towel to keep it from slipping in the following step, then set it aside until the milk is ready.

As soon as the milk starts to boil, remove it from the heat. Slowly pour about one half of the hot milk into the egg mixture in a thin stream, while whisking constantly, to temper the egg mixture. Then add the egg-milk mixture back into the hot milk in the saucepan.

Heat the custard over medium heat while whisking vigorously until the pastry cream comes to a boil. The pastry cream is boiling when you see bubbles at the surface. Once the first bubbles break the surface, keep whisking the pastry cream for about 1-1 1/2 minutes while whisking constantly. This ensures that the cornstarch cooks and thickens the custard properly. Remove from heat. Immediately add the chocolate, butter, and bloomed gelatin if using. Whisk the mixture well, until the chocolate, butter, and gelatin dissolve and mix in well. If needed, keep the pan on the stove with the heat off so the residual heat continues the melt and mix the custard together.

Strain the custard, if desired to remove any lumps, directly into a container where the pastry cream will be stored. Immediately cover the surface with plastic wrap, making sure the plastic wrap is touching the whole surface to prevent a skin from forming.

The custard can be used when it has cooled to room temperature, or let it chill in the refrigerator for a few hours or overnight. It will set when cooled, so may need to be whisked smooth before use.

Store in an airtight container for up to 4 days in the refrigerator.

Makes 3 1/2 cups.

From The Flavor Bender blog, with minor changes to instructions