ALMOND CREAM: In a nonreactive saucepan, combine the almond paste, 1 cup half-and-half and sugar. Whisk to dissolve. Place over medium heat and bring to a simmer.
In a small bowl, combine the egg yolks, cornstarch and remaining 1/4 cup half-and-half. Whisk well.
Remove the milk from the heat and add some of the hot liquid to the egg mixture and mix well. Add the egg mixture back to the simmering milk and place over the heat.
Bring to a boil, and cook for 2 to 3 minutes, whisking constantly. Remove from the heat and stir in the butter. Pour into a bowl and place a piece of plastic wrap directly on top of the pastry cream. Cool completely before using.
CHOCOLATE PUFFS: Preheat oven to 400°F and lightly coat baking sheet with cooking spray. Set aside.
In a medium sized saucepan over medium heat, combine water, butter, sugar and stir until butter is melted.
Add flour and cocoa powder all at once; stir vigorously until mixture pulls away from side of pan. Remove from heat and allow to cool slightly. Add eggs one at a time, beating well after each addition.
Place or pipe 1/4 cup of mixture onto prepared baking sheet, spacing 2" apart. Bake for 30-40 minutes until puffed and firm. Allow to cool to room temperature before proceeding.
ASSEMBLY: Using a pastry bag with a star tip, fill bag with Almond cream. Using the tip, pierce the side of a chocolate puff and begin squeezing almond cream into the center, slowly removing the tip and ending with a swirl as it exits the puff. Repeat with remaining puffs. (You can also opt to cut them in half horizontally and fill with the almond cream, then replace the tops like a sandwich).
Place on a silver platter (metal will help keep them cool), cover with plastic wrap and refrigerate. Remove plastic wrap and dust with powdered sugar just before serving.