Pre-heat the oven to 350 degrees. Line a baking sheet with parchment paper and an 8 x 8 square baking pan with parchment paper, leaving an overhang on all sides.

Melt the butter in a medium saucepan. Add the remaining ingredients and stir till all of the flour is absorbed and the mixture begins to clump. Pour the streusel onto your prepared baking sheet, spread into an even layer and break up any large clumps. Set aside.

Wipe out the saucepan.

Melt the butter in the wiped-out saucepan and continue cooking, swirling occasionally, till the bubbling subsides, the butter smells nutty and brown bits are visible on the bottom of the pan. Remove from the heat, pour into a medium mixing bowl and let cool for 5 - 10 minutes.

Add the brown sugar to the butter and beat till blended. Add the egg and vanilla and beat again. Add the flour, baking powder, salt and strawberry powder and beat till smooth. Add half the chopped ruby chocolate and half the chopped white chocolate and fold in.

Transfer the batter to your prepared baking pan and use an angled spatula to smooth into an even layer. Top with the streusel. Bake for 25 - 30 minutes till the edges are golden brown and a toothpick inserted in the center comes out clean or with just a couple of crumbs attached.

Cool the blondies in the pan on a wire rack.

Melt the remaining ruby and white chocolates in the microwave and drizzle atop the cooled blondies. Let set, cut into squares and serve.