1. Preheat oven to 400*F. Grease muffin cups or line with muffin liners.
2. Combine 1 1/2 cups flour, 3/4 cup sugar, salt and baking powder. Place vegetable oil into a 1 cup measuring cup; add the egg and enough milk to fill the cup. Mix this with flour mixture. Fold in blueberries. Fill muffin cups right to the top, and sprinkle with crumb topping mixture.
3. To Make Crumb Topping: Mix together 1/2 cup sugar, 1/3 cup flour, 1/4 cup butter, and 1 1/2 teaspoons cinnamon. Mix with fork, and sprinkle over muffins before baking.
4. Bake for 20 to 25 minutes in the preheated oven, or until done.
My Note: HELPFUL TIPS: Vanilla isn't needed for this recipe (as someone have suggested). Makes no difference ,and I put a heaping overflowing teaspoons & I've made this 50+ times. Other than that, this recipe makes me a hero at the office! They say BETTER than any bakery! I use BROWN SUGAR instead of white for the topping. When I have buttermilk, I use that in place of milk. It's important to use butter at room temp (to a point that if you put a fork through it, it would smush). This makes it a lot easier to put on top. You can substitute blueberries with any fruit & it turns out great! Be sure to use PAM on the pan or they may stick. Also, frozen blueberries do not turn out the same. Fresh Fresh! Regular size tins make 12 at 18 minute Giant tins as recommended make 5-6 so double recipe! (Update 7/08): I you have had trouble with the muffins sinking. You're are over mixing or it's from adding TOO MUCH topping to 1 muffin using the given one. If you must drown yourself in topping, try this fail proof one I use that has less butter (perfect amount if doubling recipe): 2/3C brown sugar, 1/4C flour, 1/4 tsp cinnamon, 2T butter. Use fork to mix and has nice coarse texture. Just as crunchy & delicious w/the perfect muffin EXCEPT it doesn't cause the muffins to sink!
I took a look at the recipe reviews for these muffins and incorporated suggestions. In summary, I made the recipe as printed, but I added 1/2 t. vanilla, replaced all of the milk with buttermilk and then added a few more tablespoons of buttermilk to the recipe, replaced the white sugar in the streusel topping with brown sugar, filled 12 regular-size muffin tins about 2/3 full and lightly placed the streusel on top. I then baked them in a 400*F. oven for 18 minutes. They were excellent! This recipe would be great with other types of fruit added (other berries, diced peaches, etc.) or with chocolate or white chocolate chips, etc -- .