Preheat oven to 350°.
In a medium sized bowl, combine ⅓ cup flour, brown sugar, cinnamon, and a pinch of salt. Cut in 3 Tablespoons of butter until mixture is crumbly. Set aside.
Melt remaining butter.
Peel the apple and cut into small cubes.
In a large bowl, combine remaining flour, sugar, baking powder, and pinch of salt.
Mix together egg, milk, and vanilla with the melted butter. Stir egg mixture into the flour mixture. Stir in apple.
Scoop rounded spoonfuls into muffin greased muffin tin. Top with crumb mixture.
Bake until toothpick inserted into center comes out clean, about 25 minutes. Remove from pans after 10 minutes and serve warm.
