3/4 cup butter, melted
2 3/4 cups white sugar, divided
4 teaspoons vanilla extract, divided
3 eggs
3/4 cup unsweetened cocoa powder
2 1/2 cups semi-sweet chocolate chips, divided
2 1/2 cups all-purpose flour, divided
1 teaspoon salt, divided
1 cup butter, softened
2/3 cup packed brown sugar
1/4 cup heavy cream
Line a slow cooker with a liner or aluminum foil. Spray with non-stick cooking spray.
In a large bowl, combine melted butter, 2 1/4 cups sugar, 2 teaspoons vanilla extract and eggs. Whisk until combined.
To the butter and sugar mixture, add cocoa powder, 1 cup of chocolate chips and 1/2 teaspoon salt. Add in 1 1/2 cups of all-purpose flour, and stir with a wooden spoon.
Pour the brownie mixture into a 6-quart slow cooker, smoothing out the surface.
Place the lid on the slow cooker and cook on high for 2 1/2 to 3 hours, until the brownies are cooked and set in the center.
Turn the slow cooker off and remove the lid. Allow the brownies to sit in the slow cooker for about 2 hours, or until completely cool.
While brownies are cooling, make the cookie dough. In the bowl of a stand mixer, cream together the 1 cup of softened butter, remaining 1/2 cup of sugar and the brown sugar. Beat these together for about 5 minutes until fluffy.
And in the cream and remaining 2 teaspoons of vanilla extract and beat for another 30 seconds.
Add in remaining 1 cup of flour, 1/2 teaspoon of salt and 1 cup of the chocolate chips. Mix until well combined.
When brownies have fully cooled, spread the cookie dough onto the brownies.
Top with remaining 1/2 cup of chocolate chips, pushing them into the cookie dough layer slightly so they stick.
Using the liner or foil, remove brownies from the slow cooker. Discard liner or foil, slice brownies and serve.
