Preheat the oven to 375℉/190℃. Line a pan with parchment paper and set aside.
In a large bowl, add cold butter, white sugar, baking powder, and flour. Mix together until a crumb forms. The consistency will be sand-like. Set aside 1 1/2 cups for the topping.
3 cups all-purpose flour, 1 cup butter, 1/3 cup white sugar, 1/2 tsp baking powder
With the remaining crumb, transfer it into the prepared pan. Press down firmly and evenly along the bottom and sides of the pan. Make sure it is evenly pressed down.
Bake this base for 15 minutes.
Take the remaining 1 1/2 cups of crumb and with your hands, press it to form larger and smaller streusel pieces. Place in the fridge to chill.
Slice the strawberries into pieces. Then add the white sugar and cornstarch and stir together.
Once the base has been baked, sprinkle the strawberries on top, making sure the strawberries don't touch the edges of the pan. Then sprinkle the crumb on top evenly.
Place back into the oven and bake for another 45-55 minutes. The bars are ready when the edges have turned a golden brown and the top is beginning to brown.
Allow the bars to cool completely before slicing if you want proper slices. If you want to serve it warm, it will be messy but so delicious. I prefer them warm with a scoop of vanilla bean ice cream!
Notes
Strawberries: Your strawberries need to be sweet for this recipe to taste good! There isn't a lot of sugar in the base. If your strawberries aren't the sweetest, add another 1/3 cup of sugar into the base.