1 1/2 cups unbleached all-purpose flour
1/2 cup granulated sugar
1 1/2 teaspoons baking powder
1/4 teaspoon baking soda
1/4 teaspoon kosher salt
8 Tablespoons (4 ounces) unsalted butter, melted
1 cup sour cream
1 extra large egg
1 teaspoon vanilla extract
1 cup small diced fresh strawberries
2 Tablespoons strawberry preserves, divided

Streusel Topping
makes 3 cups, enough for 4 batches of muffins

1 2/3 cups confectioners' sugar
1 1/3 cups unbleached all-purpose flour
1 teaspoon ground cinnamon
12 Tablespoons unsalted butter, cold and cubed