1-Preheat the oven to 425°F: Preheat the oven to 425°F. Line a standard muffin pan with paper liners and set aside. This recipe makes about 10-12 muffins.
2-To make the crumb topping, stir together: To make the crumb topping, stir together flour, brown sugar, and salt. Add melted butter and mix with a fork until coarse crumbs form. Set aside.
3-To make the cream cheese filling, mix: To make the cream cheese filling, mix softened cream cheese, sugar, cornstarch, and vanilla just until smooth and combined. Set aside.
4-To make the muffins, in a large: To make the muffins, in a large bowl, stir together flour, baking powder, and salt. Set aside.
5-In a medium bowl, whisk together egg: In a medium bowl, whisk together egg and granulated sugar until combined. Whisk in Greek yogurt, oil, and vanilla extract until smooth.
6-Add the wet ingredients to the dry: Add the wet ingredients to the dry ingredients and whisk just until combined. Do not overmix.
7-If the raspberries are large, cut them: If the raspberries are large, cut them in half or into smaller pieces first. Toss raspberries with 1-2 teaspoons of flour. Gently fold in about half of the raspberries. To avoid tinting the batter pink or breaking the berries too much, you can also skip mixing all the berries into the batter and add most of them by hand while assembling the muffins.
8-To assemble the muffins, spoon about 1: To assemble the muffins, spoon about 1 Tablespoon of muffin batter into each liner. Spread it slightly to cover the bottom. Add about 1 teaspoon to 1/2 Tablespoon of cream cheese filling in the center, then add a few raspberry pieces. Top with more muffin batter, filling each cup about 2/3 full, no more than 3/4 full.
9-Scatter the remaining raspberry pieces on top: Scatter the remaining raspberry pieces on top of the muffins. Generously sprinkle streusel crumbs over each muffin and gently press the crumbs to stick to the batter.
10-Place the muffins in the preheated oven: Place the muffins in the preheated oven and immediately reduce the oven temperature to 350°F. Bake for 25-30 minutes, or until the tops are golden brown and the centers are set. Baking time may vary depending on how full the muffin cups are and how juicy the raspberries are.
11-Cool the muffins in the pan for: Cool the muffins in the pan for 5-10 minutes, then transfer them to a wire rack to cool completely.
12-To make the glaze, stir powdered sugar: To make the glaze, stir powdered sugar with milk or cream. Start with 1 1/2 teaspoons of liquid and gradually add more until you reach the desired drizzling consistency. Drizzle over cooled muffins before serving.