Cream Puff Brownie Cake

For the brownie layer:
Preheat oven to 350ºF and grease an 8 by 8-inch or 9 by 9-inch pan. Alternatively, you could line the pan with parchment paper.

Melt unsalted butter and semi-sweet chocolate chips in microwave or using a double boiler. Stir until chocolate is completely melted and smooth in texture. Add granulated white sugar and mix until completely incorporated.

Add eggs in one at a time until completely blended. Add vanilla. Stir in flour until just incorporated.

Pour batter into a prepared pan and bake in a water bath for 45 minutes (reduce time if not using a water bath).

For the cream puff shells (pâte à choux):
Preheat oven to 350ºF and line a baking sheet with parchment paper.

Cut butter into small cubes and put into a large sauce pot. Add water, salt and sugar and bring to a boil over high heat. Remove from heat and add flour all at once, stirring vigorously until completely incorporated. Place pot over medium heat and stir mixture until it forms a ball of dough that does not stick to the side of the pot. Remove dough from heat and allow it to cool in a mixing bowl for approximately 5 minutes.

Add eggs one at a time, thoroughly mixing after each addition. Use a spoon to drop rounded tablespoons of dough onto a prepared baking sheet.

Place baking sheet in the oven. Turn heat up to 425ºF and set the timer for 10 minutes. Lower temperature to 350–F and bake for another 15 minutes or until shells are golden in colour. Allow cream puff shells to completely cool on a rack.

For the chantilly cream:
Place cold heavy cream into a chilled bowl. Beat on high power until cream starts to thicken slightly. Add sugar and continue to beat until cream until medium-firm peaks are formed. Mix in vanilla.

Put cream into a pastry bag using a round tip for filling the cream puff shells. Pipe cream into cooled cream puff shells by poking a hole in the bottom and fill until the shell expands slightly. Alternatively, you can cut the top off the shell, put the cream inside and replace the top.

For the chocolate ganache glaze:
Melt heavy cream and chocolate chips in the microwave or using a double boiler. Stir until chocolate is completely melted and smooth. Add sugar and vanilla and stir until smooth.

Pour glaze over cooled brownies until the top is covered of the brownies are covered with a thin layer of ganache. Cover the brownies with a layer of cream puffs in 4 by 4 or 5 by 5 rows. Drizzle the first layer of cream puffs with chocolate ganache.

Add an overlapping layer of cream puffs in 3 by 3 or 4 by 4 rows. Drizzle the second layer of cream puffs with chocolate ganache.

Add one or two cream puffs to the top middle of the cake. Drizzle with chocolate ganache and garnish with powdered sugar or white chocolate curls.

Keep cake covered in a fridge for up to 2–3 days. Store remaining cream puffs in a fridge for 2–3 days or up to two months in the freezer.