Mochi Brownies

Name: Mochi Brownies
Cuisine: American, Asian, Japanese
Ingredients: 120g unsalted butter, melted; 50g cocoa powder; 150g granulated sugar; 150g light brown sugar; 3 eggs; 2 teaspoons vanilla extract; 180g glutinous rice flour; 2 teaspoons baking powder; 1/2 teaspoon salt; 500ml whole milk (heat this in your microwave for about 1 minute, we want it to be warm so the coffee can dissolve in it); 2 teaspoons instant coffee; Flaky salt to sprinkle on top (optional)