Whisk together the melted butter and sugar in a bowl. Add the egg and vanilla extract and whisk to combine.
Add the flour, baking soda, baking powder, and salt, and mix it all together.
Fold in the white chocolate and sprinkles
Pour the batter into an 8x8 baking pan that’s been lined with parchment paper.
Bake at 350 For 25-30 minutes
Remove the blondies out of the oven and allow them to cool.
While the blondies are cooling, place candy melts in a microwave-safe bowl. Heat in 30-second intervals, stirring between each interval until fully melted. Be careful not to overheat, as this can cause the candy to burn.
Drizzle with melted candy melts over the top of the blondies. Before the candy melts harden, add additional sprinkles to the blondies.