Step 1

Heat oven to 350°F. Prepare a 9x13 baking dish with non-stick spray or GOOP.

Step 2

In a large bowl add flour, cocoa, baking powder, salt. Whisk together ingredients until they are fully incorporated.

Step 3

In the bowl of a stand mixer or in a large bowl using a hand-held mixer, beat the eggs, sugar, butter, and vanilla until light and fluffy.

Step 4

With the mixer off, add in the flour mixture. Turn mixer on low and mix until ingredients are well combined.

Step 5

Pour brownies into a prepared baking dish and bake for 30-35 minutes at 350°F. Brownies are done when an inserted toothpick is removed with crumbs but not wet batter.

Step 6

Chop dark chocolate and microwave in 30-second increments until melted. (about 1 1/2 minutes total) Set aside.

Step 7

In the bowl of a stand mixer fitted with the paddle attachment, add the butter and sugar. Turn mixer on high for 1 minute. Butter and sugar should be lighter and fluffy.

Step 8

With the mixer on low, pour in the melted (and slightly cooled) chocolate. Allow ingredients to combine for 30 seconds then turn the mixer off and scrape down the sides.

Step 9

Add vanilla and cocoa powder. Mix for about 30 seconds.

Step 10

Add in 4 eggs and turn the mixer on high for 10 minutes. The filling should lighten, increase in volume, and appear very smooth and shiny. (The filling will darken after assembly.)

Step 11

In a large bowl or in the bowl of a stand mixer, pour the heavy whipping cream. Whip (or use the whisk attachment on a hand-held mixer) for about 2 minutes, or until soft peaks occur.

Step 12

Add in confectioners sugar and whip until there are firm peaks. (Lift the whisk attachment out and make sure the whipped topping holds its shape.)

Step 13

When brownies are cooled to room temperature, pour french silk filling over top. Smooth with a small offset spatula.

Step 14

Spread whipped topping over top of the filling and smooth with an offset spatula.

Step 15

Refrigerate for at least 4 hours, preferably overnight.