Preheat oven to 350°F Line muffin pan with liners or spray with non-stick cooking spray.
In a mixing bowl, beat butter and sugar.
Add egg and vanilla, beat well.
In a separate bowl, combine flour, baking powder, and salt. Slowly add milk and flour mix, alternating between until incorporated into the butter mix.
Beat until completely combined.
Gently fold in strawberries.
Add batter evenly to muffin pan, about 1/2 cup each.
To make crumble, combine ingredients with a fork or pastry blender.
Top batter with crumble.
Bake muffins for 15-20 minutes.