Preheat the oven to 325°F and line or greast an 8x8 baking dish.
Melt the butter and white chocolate bar in a microwave safe bowl. Heat in short intervals (15 seconds each), stirring each time, until smooth and fully melting.
Mix the egg and sugar in a medium bowl with a hand held mixer until light, fluffy, and foamy (about 2 minutes).
Add the melted white chocolate mixture and vanilla into the egg mixture until smooth.
Mix in flour, baking powder and salt until combined.
Fold in both the white chocolate chips and chocolate chips into the mixture.
Pour into the prepared baking dish and spread evenly. Bake for about 30 minutes checking to make sure center is set!
Notes
Don't overbake - These white chocolate brownies are best with soft and fudgy.
Let them cool (as hard as it might be) before slicing for cleaner cuts. Use a sharp knife and clean in between cuts.
While melting the chocolate in the microwave, be sure to stir in 15-20 second increments to keep it from becoming grainy.
Use a good chocolate - Make sure to enjoy the taste of it.
Use parchment paper - this helps with easily lifting out the brownies (and it makes cleanup easier).
Storage
Refrigeration: Store in an airtight container at room temperature for up to 5 days.Freezing: To freeze these white chocolate brownies, slice them and store them in a freezer-safe container or bag. When you are ready to eat one, either warm it up in the microwave or let it come to room temperature.Make sure to separate layers with parchment paper before freezing.