In a small bowl, mix the flour, brown sugar, and cinnamon. Add in the melted butter and mix with a fork. Place in the fridge to chill while you make everything else.

Preheat the oven to 350℉. Spray a 9X9-inch baking pan with baking nonstick spray. Line the bottom and 2 sides of the pan with parchment paper and spray again. Set aside.

In a medium bowl using a hand mixer, beat the cream cheese and sugar on high speed for 1 minute. Add in the flour and vanilla and mix on medium until combined.

Add in the egg and mix on low speed until just combined. Pour in the chocolate chips and use a rubber baking spatula to mix it in. Set aside.

In a medium bowl, sift the flour, baking powder, baking soda, and salt. Set aside.

In a large bowl using a mixer, beat the butter, oil, sugar, and brown sugar on high speed for 2 minutes.

Add in the sour cream, vanilla, and eggs. Mix on medium. Add in the dry ingredients, buttermilk, and mini chocolate chips. Mix on low speed until just combined. Scrape the bowl.

Spread the cake batter into the pan and spread evenly. Use a cookie scoop to scoop the cheesecake batter into dollops on top. Use an icing offset spatula to spread the cheesecake batter evenly.

Take the crumble out of the fridge and break up any large chunks with your fingers. Sprinkle the crumble on top of the cheesecake layer.

Bake for 40-50 minutes until a toothpick inserted comes out clean.

Let the cake sit in the hot pan for 20 minutes before transferring to a cooling rack. Cool completely before icing.

In a small bowl, mix powdered sugar, milk, and vanilla. Whisk until it is a pourable consistency. Use a spoon to drizzle the icing on top of the cake.