In a medium bowl, combine 1 cup of flour, 1/4 cup of granulated sugar, and a pinch of salt. Drizzle in 1/4 cup of melted unsalted butter and mix until the mixture resembles coarse crumbs. Set aside for topping.

In a separate bowl, beat together 8 ounces of softened cream cheese, 1/4 cup of granulated sugar, 1 tablespoon of cornstarch, and 1 teaspoon of vanilla extract until smooth.

In a large bowl, whisk together 2 cups of flour, 1/2 cup of granulated sugar, 1/2 cup of light brown sugar, 1 tablespoon of baking powder, and 1/2 teaspoon of salt. In another bowl, whisk 1 large egg, 1 cup of Greek yogurt, 1/4 cup of vegetable oil, and 1 teaspoon of vanilla extract, then fold into the dry ingredients with half of the mixed berries.

Preheat oven to 375°F (190°C) and line muffin tin with paper liners. Spoon batter into cups, creating a dent for the cream cheese filling, and fill with the cream cheese mixture. Top with remaining berries and streusel.

Bake for 30-35 minutes until tops are golden and a toothpick comes out clean. Remove when ready.

Let muffins cool in the pan for 5-10 minutes before transferring to a wire rack. Drizzle with a glaze made of powdered sugar and water if desired.