Preheat oven to 350 degrees F. Line 8'x8" or 9"x9" metal baking pan with foil or parchment paper and grease it. Melt butter and chocolate in a microwave safe bowl.Stir well with a whisk until completely smooth. Add both the sugars and mix. Add eggs one at a time beating well after each addition. Stir in vanilla and then flour,baking soda ,xanthum gum and salt, just until well blended. Pour batter in prepared pan. Bake for 30 minutes or until toothpick inserted 2 inches from edge comes out almost clean. Cool completely in pan.While they are cooling, prepare frosting. In a cup dissolve coffee in water. Stir in vanilla;set aside. In a small pot, heat butter and brown sugar over medium heat until mixture melts and bubbles, about 1 minute. Remove from heat. With wire whisk, stir in coffee mixture and then confectioner's sugar. Blend with whisk until smooth. With a small metal spatula,spread warm frosting over cooled brownies. Let stand for 20 minutes to allow frosting to set slightly. When frosting has set, remove brownies out of the pan by gripping the paper edges. Peel the paper/ foil away from sides. Cut in squares.
Garnish each brownie square with white chocolate heart.
To make chocolate hearts; draw hearts on a parchment or wax paper. Place the paper, pencil side down on a cookie sheet. Melt white chocolate in a small pot over another pot of simmering water. Spoon warm chocolate into a pastry bag fitted with writing nozzle. Use this as to pipe heart shaped outlines on paper. Let hearts stand until set or keep it in fridge for 1-2 hour.