Step 1: Make the blueberry compote
Combine frozen wild blueberries, granulated sugar, light brown sugar, and lemon juice in a pot over medium heat. Cover and let the blueberries defrost while the sugars melt, stirring occasionally.

Step 2:

Step 3: Thicken the compote
Stir together cornstarch and water separately. Once the blueberry mixture is boiling, add the cornstarch mixture and stir well. Simmer for 20 to 30 minutes until thickened, then let cool completely.

Step 4:

Step 5: Prepare the graham cracker crumble
Preheat oven to 350°F and line a baking sheet with parchment paper. Mix graham cracker crumbs, sugar, and salt, then stir in melted butter until the mixture looks like wet sand.

Step 6:

Step 7: Bake the crumble
Spread the crumble mixture onto the prepared baking sheet and bake for 10 to 12 minutes until golden and aromatic. Let cool.

Step 8:

Step 9: Make the cupcake batter
Line a cupcake tin with liners. Whisk together cake flour, baking soda, baking powder, salt, and milk powder. In another bowl beat butter, oil, and sugar until fluffy. Add eggs and vanilla, then mix in the dry ingredients until almost combined. Add sour cream, then stream in the milk and mix until smooth.

Step 10:

Step 11: Bake the cupcakes
Fill each liner halfway and bake at 350°F for 13 to 15 minutes until risen and fluffy. Let cool completely.

Step 12:

Step 13: Make the buttercream
Beat butter and cold cream cheese until smooth. Add half the powdered sugar and mix, then add salt, vanilla, and the remaining powdered sugar. Beat until fluffy.

Step 14:

Step 15: Fill and finish the cupcakes
Remove the center of each cupcake about halfway down. Spoon in the blueberry filling, sprinkle with graham cracker crumble, pipe on the cream cheese buttercream, then top with more crumble and a spoonful of blueberry compote.