Step 1

Preheat the oven to 375°F with the rack placed in the center of the oven. Line a muffin pan with cupcake liners and set aside.

Step 2

In a small bowl, stir together the sugar, flour and cinnamon with a fork. Drop in the butter, and using your fingers, a pastry cutter or two forks, cut the butter into the sugar mixture until you have crumbs. Set aside.

Step 3

In a medium bowl, whisk together the flour, sugar, baking powder and salt until combined. In a small bowl, whisk together the oil, egg, buttermilk and vanilla. Add the buttermilk mixture into the flour and use a spatula to mix until just about halfway incorporated. Drop in the blueberries and mix a little bit more, just until the flour is incorporated – do not overmix the batter, you want it to be lumpy.

Step 4

Distribute the batter into the prepared muffin pan and sprinkle with the streusel. Place in the oven and bake for about 18-20 minutes, or until a toothpick inserted into the center comes out clean. Remove from oven and place the muffins on a wire rack to cool before enjoying.