Preheat oven to 350°F (180°C). Spray a 9-inch square baking pan with cooking spray. Line pan with parchment paper, letting excess extend over sides of pan.

In a medium bowl, whisk together flour, baking powder, and salt.

In a large bowl, whisk together melted butter and brown sugar until well combined; whisk in eggs and 1 teaspoon (4 grams) vanilla. Add flour mixture, and fold just until combined. Fold in 4 ounces (113 grams) white chocolate and diced strawberries. Spread batter into prepared pan. Top with sliced strawberries and remaining 1 ounce (29 grams) white chocolate, gently pressing into batter.

Bake until golden brown and a wooden pick inserted in center comes out with a few moist crumbs, 40 to 45 minutes. Let cool completely in pan on a wire rack. Using excess parchment as handles, remove from pan.

In a small bowl, whisk together confectioners’ sugar, 1 tablespoon (15 grams) water, and remaining¼ teaspoon (1 gram) vanilla until smooth. Cut blondie into pieces, and drizzle with glaze. Refrigerate in an airtight container for up to 3 days.