Preheat oven to 375F and butter a muffin tin, or line with muffin tin liners.
If you are using the streusel topping, make it first. Combine the ingredients with your fingertips until it is crumbly and the butter is completely incorporated. The mixture will be dry. Set aside.
In a large mixing bowl, whisk together the eggs, oil, sugar, buttermilk, and extract. Get everything well combined.
Whisk in the baking powder, baking soda, and salt. Then fold in the flour. When the flour is almost all incorporated, fold in the berries.
Fill your muffin cups quite full, and then sprinkle lightly with streusel mixture. Add sparkling sugar on top of the streusel. Bake in a preheated oven for about 25-27 minutes, or until risen and just turning golden. Different ovens vary greatly, so check these on the early side.
Cool slightly before turning the muffins out of the pan. Devour warm, with plenty of butter.