Preheat your oven to 425°F and grease a standard 12-cup muffin pan with butter or cooking spray. While the oven heats, hull and dice the strawberries into 1/2-inch pieces and set them aside. Cube the cold butter into 1/4-inch pieces for the streusel topping and set aside. Having everything prepped and ready before you start mixing will keep your workflow smooth and prevent the batter from sitting too long.

In a small bowl, combine the brown sugar, flour, cinnamon, and cold cubed butter. Using a fork or your fingertips, work the mixture until it resembles coarse crumbs with some pea-sized pieces of butter still visible. This texture is key to creating a crispy, crumbly topping. Set aside while you prepare the batter.

In a large mixing bowl, combine the melted and cooled butter with the sugar and brown sugar. Beat for about 2 minutes until the mixture is light and slightly fluffy. Add the eggs one at a time, mixing well after each addition, then add the yogurt and vanilla. Beat until the mixture is smooth and well-combined. I find that using Greek yogurt like Fage gives the muffins a wonderful tender crumb and keeps them moist without being dense.

In a separate bowl, whisk together the flour, baking soda, baking powder, salt, and nutmeg. Add the dry ingredient mixture to the wet ingredients from Step 3 and fold gently until just combined—don't overmix, as this can lead to tough muffins. Gently fold in the diced strawberries, being careful not to crush them, so they stay intact and distribute evenly throughout the batter.

While the main batter rests, beat the cream cheese in a small bowl until smooth and creamy. Add the egg yolk, vanilla, and sugar, then beat until the mixture is light and fluffy with no lumps. I always use Philadelphia cream cheese because it has the best texture and creates a perfectly smooth filling that doesn't overpower the strawberry flavor. Set aside until ready to layer.

Divide the strawberry batter from Step 4 among the 12 muffin cups, filling each about one-third full. Drop a spoonful of the cream cheese filling from Step 5 into the center of each cup, then top with more strawberry batter until the cups are nearly full. Divide the streusel topping from Step 2 evenly among the muffins, sprinkling it over the top of each one and pressing it down gently so it adheres to the batter.

Place the muffin pan in the preheated 425°F oven and bake for 5 minutes to set the outer structure. Then lower the oven temperature to 350°F and continue baking for 18-20 minutes more, until a toothpick inserted into a muffin (avoiding the cream cheese center) comes out clean or with just a few moist crumbs. The high initial heat helps create a nice rise, while the lower temperature ensures the centers cook through without the tops burning. Let the muffins cool in the pan for 10 minutes, then transfer them to a wire rack to cool completely.