Sift the flours and baking powder into a large bowl, then stir in the sugar and make a well in the centre. Whisk together the eggs, milk and liqueur, if using, in a jug, then pour into the well. Whisk together, gradually incorporating the flour from the edges until the batter is smooth. Stir in the mashed bananas and chocolate chips.
Heat the butter and a little oil in a large, nonstick frying pan, add small ladlefuls of the batter and cook for 2–3 minutes until bubbles start to appear on the surface, then flip over and cook for a further 30–60 seconds until golden. Repeat with the remaining batter to make about 20 small pancakes, adding more butter and oil to the pan if necessary.
Serve warm with scoops of ice cream and drizzled with warmed chocolate sauce, if liked.