Preheat oven to 350 degrees and grease a springform pan
In a medium bowl, combine the crumb topping ingredients. Using a fork, pastry cutter or hands, cut the butter into the flour and sugar until it resembles large crumbs; set aside
Cream together butter, sugar, eggs, vanilla and mascarpone
Add flour, baking powder, baking soda and salt and stir to combine
Gently fold in chopped strawberries
Pour into greased springform pan (you can also use a 9x9 inch square baking dish
Sprinkle crumb topping evenly over the top of the batter
Bake at 350 degrees, for about one hour; until toothpick inserted in center comes out clean
Cool before removing springform outer circle, and let cool well before cutting