Using your fingers, pinch the butter into the mixture gently until small clumps form and are about the size of a pea. Place in the fridge while you make the muffin batter.

Preheat the oven to 425° F and line a 12 cup muffin tip with muffin liners.

Take out 2 medium sized bowls. In one bowl, add the 3 cups flour, 1 cup sugar, 3 tsp baking powder, 1 tsp baking soda, and 1/2 tsp kosher salt. Mix lightly with a whisk.

Cut the blackberries in half and toss them lightly in the dry mixture.

All at once, add the dry ingredients into the wet ingredients. Using a large spatula, lightly and gently fold in the flour taking care not to over mix or mix too hard. You want the flour to JUST mix in till there are no mare large streaks. The batter will be lumpy.

Using an ice cream scoop for accuracy, scoop the batter into the prepared muffin tin all the way to the top.

Sprinkle the streusel on top of the muffins. Be generous! It’s ok if there’s a lot on the muffin tin.

Bake for 7 minutes on 425, then lower the temperature to 350°F and continue to bake for another 13-14 minutes.

Take the muffins out and let them cool for 10 minutes in the tin, then remove and cool completely on a wire rack.