Directions

1. Prepare streusel topping: In a medium bowl, stir together brown sugar, flour, and salt. With a pastry blender or two knives, cut in butter until mixture resembles large coarse crumbs; refrigerate until ready to use.
2. Preheat oven to 350 degrees. Prepare muffins: Butter and flour a jumbo 12-cup muffin tin (or two 6-cup muffin tins). In a small bowl, whisk together flour, baking powder, and baking soda; set aside.
3. Using an electric mixer on medium speed, beat together butter, sour cream, granulated sugar, and vanilla until light and fluffy. Beat in eggs, one at a time, until well combined. With mixer on low, beat flour mixture into butter mixture.
4. Divide half the batter among prepared muffin cups. Top with half the streusel mixture, then remaining batter, and top with streusel. Bake 25 to 30 minutes or until a toothpick inserted in center of a muffin comes out clean. Cool in pan 5 minutes, then transfer to a wire rack to cool completely. Dust with confectioners' sugar, if desired.