Preheat your oven to 350°F (175°C) and prepare a muffin tin by greasing it or lining with paper liners.

In a large bowl, whisk together 2 cups of all-purpose flour, ¾ cup of sugar, 2 teaspoons of baking powder, and 1 teaspoon of cinnamon.

In a separate bowl, whisk together 1 cup of milk, ⅓ cup of vegetable oil, 1 large egg, and 1 teaspoon of vanilla extract.

Gently pour the wet mixture into the dry ingredients and fold together until just combined, leaving the batter slightly lumpy.

Fill each muffin cup in the tin about two-thirds full with the batter.

In a small bowl, combine ¼ cup of cold butter, ⅓ cup of brown sugar, and ¼ cup of additional flour until the mixture resembles coarse crumbs.

Sprinkle the crumb topping over the muffin batter in the tin evenly.

Bake in the preheated oven for 20 to 25 minutes or until tops are golden brown and a toothpick comes out clean.

Let the muffins cool in the tin for about 5 minutes, then transfer to a wire rack to cool completely.