In a medium bowl, combine 1 cup of all-purpose flour, 1/3 cup light brown sugar, and a pinch of salt. Pour in 1/4 cup melted unsalted butter and mix until the mixture resembles coarse crumbs. Set aside.

In a separate bowl, combine 8 ounces of cream cheese, 1/4 cup granulated sugar, 1 tablespoon cornstarch, and 1 teaspoon vanilla extract. Beat with an electric mixer on medium speed until creamy and smooth, about 2-3 minutes.

In a large mixing bowl, whisk together 2 cups of all-purpose flour, 1 tablespoon baking powder, and 1/2 teaspoon salt. In another bowl, whisk together 1 egg, 3/4 cup granulated sugar, 1 cup Greek yogurt, and 1/4 cup vegetable oil until smooth.

Gradually fold the wet ingredients into the dry ingredients, mixing just until combined.

Gently fold in 1 cup of fresh or frozen blueberries and 1 cup of raspberries into the muffin batter.

Preheat your oven to 350°F. Line a muffin tin with paper liners. Spoon the muffin batter into the cups, filling them about two-thirds full. Create a small well in the center of each muffin and dollop in the cream cheese filling. Top with remaining berries and sprinkle with crumb topping.

Place the muffin tin in the preheated oven and bake for 30-35 minutes, or until golden brown and a toothpick comes out clean.

Cool in the tin for about 5 minutes before transferring to a wire rack. Mix 1/2 cup powdered sugar with a splash of milk or cream to create a glaze. Drizzle over warm muffins before serving.