Preheat oven to 325F (160C).

Combine chocolate and butter in a microwave-safe bowl.

Microwave on HIGH for 2 minutes, or until the butter is melted.

Stir until the chocolate is completely melted and smooth.

Add sugar, eggs, and vanilla to the melted chocolate mixture.

Mix well until fully incorporated.

Stir in flour until just combined; do not overmix.

Spray a 9-inch pie plate with cooking spray.

Spread the brownie batter evenly onto the bottom of the pie plate.

Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out with fudgy crumbs. Avoid overbaking.

Use the back of a large spoon to gently create a slight depression in the center of the brownie.

Allow the brownie to cool completely.

In a separate bowl, whisk together the pudding mixes and cold milk for 2 minutes until well combined.

Let the pudding mixture stand for 2 minutes to thicken.

Spread the pudding evenly over the cooled brownie base.

Refrigerate for at least 30 minutes before serving to allow the pudding to set completely.