• Preheat oven to 350 degrees F. Grease lightly a 9" round cake pan and line with a round piece of parchment paper

For the filling

• Add the sugar and cocoa powder to a small bowl and whisk together. Set aside along with the chocolate chips.

For the crumble topping

• In a bowl, whisk the flour, sugar, cocoa powder, powdered sugar, and salt. Add cubed butter and vanilla. Use a fork to gently cover all the butter and then, work butter into mixture until a sand like texture forms. Stir in ¼ cup chocolate chips. Set aside.

For the cake

• In a large bowl, add the flour through the espresso powder (if adding). Whisk to combine. Add in the cubed vegan butter and using a mixer, mix for 2 minutes until a sand like texture forms.
• Add applesauce and vanilla and beat until a thick mixture forms. Add in chocolate milk and vinegar and mix until a smooth consistency. Careful not to overmix.

Assembling

• Pour half the batter into the prepared cake pan and spread out to the edges. Sprinkle the filling evenly over the batter, then the reserved ¼ cup chocolate chips.
• Pour remaining batter and carefully spread to the edges. Okay if a little filling gets mixed in. Tip: We find that dollaping the remaining mix helps here instead of pouring all the the center.
• Sprinkle crumble topping all over the batter.
• Bake for 45-55 minutes. A toothpick should come out mostly clean. Remove and allow to sit for 20 minutes before cutting to allow the cake to set.
• Store at room temperature. Can be frozen.