Preheat the oven to 350 F. Line 2 baking sheets with parchment paper.
Place the butter and sugars in a stand mixer fitted with a paddle attachment. Beat on medium-high speed until light and fluffy, 3 to 4 minutes. Add the egg and vanilla and mix again.
Slowly mix in baking powder, soda, salt and flour, being careful not to over mix. I usually stop when I still have some flour remnants around the bowl.
Finely dice strawberries and mix with ½ teaspoon of flour. Fold into the cookie dough. It will get a bit wet/sticky from the strawberry juices.
Scoop the dough into 3 tbsp size balls and place 6 cookies on cookie sheet.
Mix together flour, both sugars and salt in a small bowl. Add melted butter and mix together with a fork or your fingers until it all comes together. Take a handful of the crumb topping and press it onto the top and sides of the cookie dough. Sprinkle with coarse sugar.
Chill the dough for 10-15 minutes to help firm it up before baking.
Bake for 12-14 minutes, or until the edges start to turn golden brown and middles look cooked. Run a spoon or spatula around the freshly baked cookies to help shape a perfect circle. Allow to cool completely before eating.
