Preheat oven to 350°F. Grease and line an 8x8 inch pan and place on top of a cookie sheet or two 5 inch cake rounds.
In a large bowl, add flour, glutinous rice flour, cocoa powder, salt, and baking powder. Sift together well.
In a large bowl, mix together egg, instant coffee powder and vanilla on high speed until foamy. Then add sugar. Continue to mix until it becomes light in color and voluminous.
Finely chop chocolate and put it and the unsalted butter into a small microwave safe bowl. Zap for 30 seconds, stir, then continue in 10 second intervals, mixing between each interval until melted.
Slowly add ½ room temperature milk to the chocolate until combined. Add the chocolate mixture to the egg mixture, and mix up on high until well incorporated.
Next, add half of the dry mixture and half of the remaining 1 cup of milk. Mix on low speed until just incorporated then add the rest of the dry and milk ingredients. Continue to mix on low until the last streak of flour is gone.
With a spatula do one final scrape and fold of the batter to ensure no flour pockets are remaining.
Pour into prepared pan. Fill the cookie sheet with water, leaving about ¼ inch clearance from the rim of the cookie sheet. (NOTE: this batter is very thick, don’t worry if you can’t spread it evenly in the pan, the heat of the oven will smooth everything out.)
Place in oven and bake for 35-45min mins. Once a skwerer can be inserted and removed clean, it is done.
Important! Let cake cool completely in pan before removing.