Preheat over to 375 F.
Line muffin pan with liners.
Beat butter and sugar in a mixing bowl.
Beat in egg and vanilla. The mixture will be a bit lumpy, that's okay.
Combine flour, baking powder, and salt in a separate bowl.
Slowly add buttermilk and flour mix, alternating between until incorporated in the butter mix.
Beat until completely combined.
Gently fold in about half OR ALL of the strawberries. See notes.
Add about 1/4 cup of batter to each muffin liner.
Load up the tops of the muffins with remaining strawberries.
In a mixing bowl, beat crumble ingredients until it looks like, well... a crumble.
Sprinkle crumble on the tops of the muffins.
Reduce oven heat to 350 F.
Bake muffins for 18-20 minutes.