• Preheat the oven to 350 F (180 C) for conventional oven. Please lower the temperature by 20 F (15 C) for a convection oven
• Oil a 8 x 8 inch square metal cake pan and line with parchment paper sling, overhang on the side for easier removal

Prepare brownie batter:

• In a mixing bowl, add powdered sugar, mochiko flour, and salt and just mix to combine. Set aside
  
• Combine cocoa powder, instant coffee, and milk in a saucepan. Whisk until combined. Put this on the stove over medium heat. Add butter cubes and cook until the butter melts and mixture starts to come to a boil. Lower the heat to simmer and let it cook for about 5 minutes
  
• Pour the hot milk over the flour mixture
  
• Vigorously start stirring it with a sturdy spatula for a full 2-3 minutes. You will need it to really beat the batter so it gives that springy texture and to avoid that "starchy" taste of glutinous rice flour/mochiko flour. Alternatively, you can do this with a stand mixer fitted with a flat beater (beat it on medium speed for about 2 minutes)
  
• Then add egg, one at a time
  
• Continue to mix until all eggs are in and the batter is smooth and nicely combined
  
• Scrape the batter into the prepared pan and smooth it out with rubber spatula
  

Bake:

• Bake in the middle rack for 40-50 minutes or until the center spring back when you gently press on it. There is no need to do a toothpick test as it won't be accurate
  

Cool down:

• Let the brownies cool down in pan for at least 10 minutes. Then transfer to a cooling rack to let it cool down completely before cutting
  
• The cake will be "puffy" when it first gets out of the oven, but it will shrink down a bit after cooling down, and that's normal