Brownie Bottom Cookie Dough Cheesecake

Brownie Bottom Cookie Dough Cheesecake (adapted from The Chunky Chef)
Brownie layer:
1 stick unsalted butter (softened)
3/4 cup semi-sweet chocolate chips
1 cup sugar
2 eggs
1/4 cup milk
1 cup flour

Cheesecake Layer:
3 (8oz) pkg of cream cheese
1 cup sugar
4 eggs
1 tsp vanilla
1/2 cup sour cream or greek yogurt
1 Tbsp flour

Cookie Dough Layer:
1 stick margarine (softened/almost melted)
1/2 cup brown sugar
1/4 cup white sugar
2 Tbsp. milk
1 tsp vanilla
1 1/4 cup flour
1/2 cup mini chocolate chips

Chocolate topping:
1/3 cup MILK chocolate chips
1 tsp vegetable oil

Prepare a 9″ spring form pan by covering bottom with parchment paper and then spraying with cooking spray. Preheat the oven to 350*.
To make the brownie layer, in a saucepan melt the butter and chocolate until smooth, stirring often. Remove from heat and stir in sugar. Allow to cool for 5 minutes, stirring occasionally to help speed up the process.
In a bowl combine chocolate mixture, milk, and eggs. Then add in flour until combined. Pour batter into prepared pan and bake for 25-28 minutes. (Once brownie is removed from oven, reduce oven temp. to 325*.)
Begin the cheesecake layer with cream cheese and eggs that have been allowed to come to room temperature. Combine cream cheese and sugar and vanilla until smooth. Then add sour cream or greek yogurt (I would normally recommend using plain greek yogurt, but all I had this time was vanilla greek yogurt which worked fine!). Add each egg, one at a time. Remember to scrape down the sides of your bowl with a spatula. Lastly, gently mix in the 1 Tbsp of flour. Pour in pan over brownie crust, Bake for 50 minutes; or until the middle is still ‘jiggly’ but the rest/outer edge is set. (Take a knife and run around rim of cheesecake to help prevent cracking as it cools and pulls away from edge of pan.)
Cool gradually in oven for 30 min or so, less time if appears to begin cracking. Then cool on counter further before placing in refrigerator. I cooled for several (4?) hours before adding the cookie dough and chocolate topping.
To prepare cookie dough, simply combine all ingredients in the order listed. Then spread over top of chilled cheesecake. Melt the milk choc. Chips and vegetable oil in microwave safe bowl and drizzle over the top of the cookie dough layer. I placed melted chocolate in piping bag so that I had more control over where the chocolate went; but this would not be necessary.
Enjoy!