Using a small food processor or mini-chopper, add the strawberries and cornstarch. Puree until smooth.

Transfer strawberries into a small sauce pan. Place over medium-high heat, stirring occasionally, until mixture begins to boil. Boil for 2 minutes, stirring constantly. Set strawberry sauce aside.

Using an electric mixer, beat the cream cheese on medium speed until completely smooth (~3 minutes).

Add the sugar and mix well. (Tip: Don’t forget to scrape the bottom and sides of the mixing bowl to fully incorporate the sugar.)

Add flour and mix well.

Whisk the eggs and egg yolk together and add to the bowl in 2 additions, mixing fully after each addition.

Add the sour cream and vanilla. Mix until fully combined. (Tip: Use a spatula to scrape the sides and bottom of the bowl to ensure the filling is fully mixed.)

Preheat oven to 350°F.

Grease and flour a 9”x13” baking pan. Line bottom of pan with parchment paper; set pan aside.

Using a medium saucepan, add the butter, unsweetened chocolate and 1 cup of chocolate chips. Place over medium-low heat, stirring often, until butter and chocolate have fully melted; set pan aside to cool.

In a large bowl, mix together the eggs, sugar and vanilla. Stir the egg mixture into the warm (not hot!) chocolate mixture.

In a medium bowl, sift together the flour, baking powder and salt. Stir the flour mixture into the chocolate mixture.

Stir the remaining ¾ cup of chocolate chips into the batter.

Remove ½ cup of brownie batter; set aside. Pour remaining batter into prepared baking pan. Pour cheesecake mixture over brownie batter. Make 5-6 alternating lines of strawberry sauce and brownie batter on top of cheesecake layer. Use a toothpick or skewer to gently swirl the lines together.

Bake at 325°F for 50-60 minutes, or until top of brownies is just set and a toothpick comes out mostly clean.

Let cool before slicing. (Tip: If you refrigerate these brownies, they’ll be easier to slice.)