Place the chopped strawberries in a medium-sized bowl. Sprinkle with 2 teaspoons of sugar and mix well. Let stand for 30-45 minutes, then drain the excess juices.
Meanwhile, preheat the oven to 350ºF (180ºC). Line an 8-inch square baking pan with parchment paper, leaving a couple of inches of overhang to serve as handles to lift the blondies out of the pan.
In a separate medium-sized bowl, whisk together the flour, baking powder and salt until well blended.
In a large bowl, whisk together the remaining 1/4 cup (50g) of sugar, the brown sugar, melted butter and vanilla until smooth. Add the egg and the egg yolk and whisk until smooth and well combined, about 2-3 minutes. Stir in the flour mixture, just until combined. Fold in the white chocolate chips and the strawberries.
Transfer the batter to the prepared baking pan. Bake until the top looks golden brown all over and a toothpick inserted into the center of the blondies comes out with a few moist crumbs on it, about 28-33 minutes. Let cool completely in the pan. Remove the cooled blondies from the pan and cut into squares.