1/2cupsemisweet chocolate chips or dark chocolate melting wafers(85g)
Preheat oven to 325F
Prepare brownie batter according to Best Ever Brownies instructions (or package instructions, if using box-mix).
Spread evenly into the bottom of a greased and floured 9x13 pan (alternatively, line the pan with foil and then lightly spray with cooking spray -- this will make it easy to lift the brownie/cheesecake out of the pan and make clean cuts once its cooled).
Bake on 325F for 20 minutes, or until center is almost set (it should not still be liquid, and the edges will appear somewhat cooked).
As the brownie layer bakes, prepare your cheesecake.
In a stand mixer (or in a large bowl with a hand-mixer), beat together softened cream cheese and sugar, scraping down the sides with a spatula occasionally to ensure it is mixed well. (beat on medium-speed about 1-2 minutes, scraping down side occasionally, it should be creamy and well-mixed).
Add sour cream & mix well, stopping once to scrape down the sides before mixing again.
Add eggs, one at a time, beating until just mixed after each addition (and scraping down the sides after each addition)
Stir in vanilla extract.
Once brownie layer has finished baking (do not turn off your oven), evenly, gently, spread the cheesecake over the brownie layer.
Bake on 325F for 40 minutes, or until center is set (not liquidy, bounces back to the touch).
Allow to cool to room temperature, and then place in refrigerator for at least 6 hours before cutting and serving.
Chocolate Drizzle (optional)
After cooling and cutting cheesecake squares, melt chocolate in a microwave-safe bowl on 15 second increments (stir well in-between) until melted.
Use a spoon to drizzle chocolate over bars or, for neater design pour chocolate into a Ziploc bag and snip off a small corner. Immediately pipe over squares as desired.
Return to refrigerator for several minutes until chocolate sets.