Preheat oven to 350º. Line muffin pan with paper muffin liners.
In a small bowl, whisk together flour, baking powder, and salt. Set aside.
In a large bowl, beat butter and sugar until light and fluffy. Add eggs and beat in. Add the vanilla and milk and combine well. Add flour mixture and stir until just combined.
Gently fold in blueberries. Divide batter evenly into 12 muffin cups.
To prepare streusel topping mix with sugar, flour, butter, and cinnamon with a fork. Sometimes I use my hands to get it fully incorporated so that it has the texture of wet sand. Sprinkle muffins with streusel topping.
Bake at 350º for 20 to 25 min, until a tester inserted into the center comes out clean. Makes 12 muffins.