Instructions

For cake

1. Preheat oven to 350. Generously grease and flour a 3 six-inch circular baking pans.
2. Place cake mix, sour cream, oil, eggs, and vanilla in mixing bowl. Blend with mixer on low speed for 1 minute. Stop machine, scrape down sides of bowl. The batter should look well combined and thickened.
3. Pour the batter into prepared pans. Place in oven.
4. Bake the cake until it is light brown and springs back when lightly pressed with your finger, 35-40 minutes. Remove pan from oven and place on wire rack to cool for 20 minutes. Run a dinner knife around edge of cake and invert it onto wire rack.

For Cheesecake

1. 1. Preheat the oven to 300°. In the bowl of a standing mixer, paddle the cream cheese on low until smooth, about 2 minutes. Take the zest from one lemon and rub it into the sugar, until you can smell it and the sugar has absorbed the moisture. Add the sugar and mix until it is completely incorporated, 1 to 2 minutes.
2. 2. In a small bowl, gently whisk together the cornstarch and salt. Add the milk in a slow, steady stream, then whisk in the egg.
3. 3. With the mixer on medium-low speed, add the egg mixture to the cream cheese, beating until the mixture is smooth, about 3 to 4 minutes. Scrape down the sides of the bowl.
4. 4. Pour the cheesecake batter into an 8-inch-square baking pan lined with plastic wrap. Place the pan in the oven. Bake for 15 minutes. After 15 minutes, gently shake the pan: The outside edges should be firm and the center loosely set. If the cheesecake has not reached that consistency, allow it to cook for an additional 5 minutes.
5. 5. Remove the cheesecake from the oven, set aside to cool completely.

For crumb

1. Preheat oven to 225 degrees. Line a baking sheet with parchment paper; set aside.
2. In a medium bowl, whisk together 2 tablespoons plus 1 1/2 teaspoons milk powder, flour, cornstarch, sugar, and salt. Stir in melted butter until well combined. Spread mixture on prepared baking sheet and transfer to oven. Bake until dried and crumbly, 8 to 10 minutes. Remove milk crumble from oven and let cool completely.
3. Transfer milk crumble to a large bowl and fold in remaining 2 tablespoons plus 1 1/2 teaspoons milk powder and white chocolate. Use immediately or transfer to an airtight container and keep refrigerated until ready to use.

For Blueberry Frosting

1. In a food processor, grind dried blueberries into a powder. In a separate bowl, beat butter until fluffy. Add salt and 1.5 cups sugar and blend. Add blueberry powder and blend. Continue adding powdered sugar until desired thickness is reached. Taste, and add more salt if necessary.

For Assembly

1. Layer the cake. Vanilla cake, spread liquid cheesecake, sprinkle with crumb, repeat. On the last layer, just put cake on and cover generously in blueberry frosting.