In a large bowl, use your hands or a spoon to combine the flour, sugar, cinnamon, and butter. Combine well. Set aside
Blueberry Muffins
Preheat the oven to 375 degrees F. Line a cupcake pan with paper liners, set aside.
Using either a stand mixer or an electric hand mixer, cream together the shortening, sugar, and vanilla in a mixing bowl.
Add the eggs, one a a time, mixing after each addition. Use a rubber spatula to scrape the bottom and sides of the mixing bowl occasionally.
Mix in the sour cream and milk. Add the flour, baking powder, and salt. Mix until combined. Scrape the bottom and sides of the bowl again.
Fold in the blueberries with a rubber spatula.
Scoop the batter evenly into paper liners, about three-fourths full.
Spoon a heaping tablespoon of crumb (streusel) topping on each muffin.
Bake for 25-30 minutes in the preheated oven. Or until the tops are golden and a toothpick when inserted comes out clean.
Let cool slightly before removing the muffins from the baking pan. Let cool completely.
Notes
Blueberry Muffins:
Do not over mix the batter. Mix just until everything is combined. Carefully fold in the blueberries with a rubber spatula.Use either fresh or frozen blueberries. (Do NOT thaw the berries)
How to Freeze Blueberry Muffins:
Let the muffins cool completely. Wrap individually with plastic wrap. Then plop into a large freezer-style Ziploc bag. They will last up to 1 month in the freezer.