Prepare the Crumb Topping: In a medium bowl, combine the flour, brown sugar, granulated sugar, cinnamon, and cold butter. Use a pastry blender or your fingers to cut the butter into the dry ingredients until the mixture resembles coarse crumbs. Set aside.
Preheat Oven and Prepare Muffin Tin: Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or grease it well.
Mix Dry Ingredients: In a large bowl, whisk together the flour, sugar, baking powder, and salt.
Combine Wet Ingredients: In a separate bowl, whisk together the milk, vegetable oil, eggs, and vanilla extract.
Combine Wet and Dry Ingredients: Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix; a few lumps are okay.
Fill Muffin Cups: Fill each muffin cup about 2/3 full with batter. Use an ice cream scoop or a spoon to ensure even distribution.
Add Crumb Topping: Generously sprinkle the crumb topping over each muffin.
Bake the Muffins: Bake for 18-20 minutes, or until a wooden skewer inserted into the center comes out clean.
Cool and Serve: Let the muffins cool in the muffin tin for a few minutes before transferring them to a wire rack to cool completely. Serve and enjoy!