Begin by chopping the strawberries into small, even pieces. Arrange them in a single layer on paper towels and allow them to dry. This step helps prevent excess moisture in the batter.

In a medium mixing bowl, combine the flour and brown sugar. Add the cold, cubed butter. Using a pastry cutter or your fingertips, work the butter into the dry ingredients until the mixture resembles coarse crumbs. Cover and refrigerate until ready to use.

In a clean bowl, beat the softened cream cheese until smooth and creamy. Scrape down the sides of the bowl as needed to ensure even blending. Add the granulated sugar and continue beating until light and fluffy. Mix in the egg yolk and vanilla extract until fully combined. Cover and refrigerate.

Preheat your oven to 425°F (220°C). Line 16 muffin cups with paper liners to prepare for assembly.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside. In a separate large bowl, beat the softened butter and granulated sugar with an electric mixer on medium speed until light and fluffy, approximately 2 minutes. Reduce the speed to low and add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

Gradually alternate adding the flour mixture and sour cream to the butter mixture, beginning and ending with the flour mixture. Before adding the final portion of flour, toss the chopped strawberries with the remaining flour to coat evenly. Gently fold them into the batter until just combined and no dry streaks remain.

Spoon the muffin batter into each prepared muffin cup, filling about halfway. Add one tablespoon of the cream cheese filling to each. Then, top with the remaining muffin batter, filling the cups nearly to the top.

Alternatively, for an easier option, fill each muffin liner almost completely with batter. Transfer the cream cheese filling to a piping bag, insert the tip approximately 1 inch into each muffin, and pipe about one tablespoon of filling into the center.

Sprinkle the prepared streusel evenly over each muffin. Press lightly to ensure the streusel adheres to the batter.

Place the muffin tray in the preheated oven and bake for 5 minutes at 425°F (220°C). Without removing the muffins, reduce the oven temperature to 350°F (175°C) and continue baking for an additional 15 to 18 minutes, or until the tops are golden and a toothpick inserted near the edge comes out clean.

Allow the muffins to cool in the pan for 5 to 10 minutes before transferring them to a wire rack to cool completely. Once cooled, they are ready to serve and enjoy.