For the Streusel

• In the bowl of a stand mixer fitted with the paddle attachment, combine all the ingredients. Mix on medium speed until the butter is blended with the dry ingredients and the mixture has a crumb-like texture. Set aside.
• Preheat the oven to 350ºF.  Line a standard 12-cup muffin tin with paper liners. In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt. In a separate bowl, combine the butter, sour cream, eggs, and vanilla. Gently mix the wet ingredients into the dry ingredients just until the mixture comes together. The mixture will be more like a dough than a batter. Fold in the strawberries. Evenly fill the muffin tins (I use a 2-ounce ice cream scoop). Push 1/2 teaspoon of strawberry preserves into the center of each batter mound, pushing below the surface. Using a skewer, swirl the preserves through the batter using a figure-eight motion. Top each muffin with 1 tablespoon of the streusel topping.  Bake for 30 minutes. Allow the muffins to cool in the tin for 5 minutes. Remove the muffins and cool completely.  Enjoy!