Dissolve the instant coffee in boiling water and leave aside to cool.
I like to buy a block of dark chocolate and chop into chocolate chips myself, remember if they are too large they will sink to the bottom of the batter. If you buy ready made chocolate chips that is fine as well. Mix the chocolate chips, rice flour and baking powder together in a mixing bowl and set aside.
Using an electric mixer, cream the butter and sugar together at a medium to high speed until pale and fluffy. Slowly add the beaten eggs while continuing to mix the butter and sugar.
Once the eggs are combined into the butter and sugar mix, add the flour and chocolate about a third at a time. Mixing on a slow speed the whole time. Finally add your instant coffee while mixing on a high speed.
Spoon into muffin cases and bake for 25minutes.