In a large shallow baking dish combine the eggs, Baileys and milk and stir to combine. Soak the sliced banana bread in the egg mixture, flipping to coat evenly until the bread has absorbed all of the liquid.
Heat a large non-stick frying pan over medium heat and add the butter. When the butter is melted and foaming, add the soaked banana bread to the pan and cook for 2-3 minutes each side, until crisp and golden.
While the french toast cooks, prepare the Baileys cream. Combine the cream and Baileys in a large bowl along with sugar to taste. Whisk to soft peaks and set aside.
Divide the banana bread between two places, scatter over a few slices of fresh banana and top with a dollop of Baileys cream. Finish with a scattering of walnuts (if using) and a light dusting of icing sugar. Serve immediately.