IngredientsFor the cake150g unsalted butter2 tsp espresso grounds250g banana flesh (from about 3 medium ripe bananas)90g light brown sugar40g dark brown sugar40g malted milk powder (e.g. Horlicks)100g full-fat Greek yoghurt or sour cream2 large eggs, at room temperature1 tsp vanilla extract230g plain flour1 tsp baking powder½ tsp baking soda½ tsp fine sea salt100g toasted walnuts, roughly choppedFor the espresso icing120g icing sugar, sifted1 tbsp (20ml) cooled, strong espresso coffee15g unsalted butter, very softpinch of fine sea saltMethodStep 1Grease and line the base and sides of a standard loaf tin (about 20cm x 10cm) with baking paper.Step 2Place the butter in a large saucepan over medium heat. Once melted, it will foam and sputter before settling down. Continue cooking, swirling the pan occasionally, until the milk solids at the bottom turn deep golden-brown and the butter smells nutty (about 5 minutes in total). Remove from the heat immediately (butter can go from browned to burnt quite quickly), stir in the espresso powder and leave to cool for 5 minutes.Step 3Preheat the oven to 170C fan-forced (190C conventional). Mash the bananas, then add to the browned butter along with both sugars and the malted milk powder. Whisk to combine, then add the yoghurt (or sour cream), followed by the eggs and vanilla. Whisk until smooth and combined.Step 4Sift together the flour, baking powder, baking soda and salt. Add to the wet ingredients and whisk until almost combined. Fold through 80g of the walnuts, reserving the remaining 20g for the top.Step 5Scrape the batter into the prepared tin and bake for about 50 minutes or until a skewer inserted into the centre comes out with a few moist crumbs attached. If the top iscolouring too quickly, loosely cover with foil for the final 15 minutes. Leave to cool in the tin for 15 minutes before transferring to a wire rack.Step 6For the icing, whisk together the icing sugar, espresso, softened butter and salt in a mixing bowl until smooth and thickly pourable. Step 7Spoon the icing over the loaf while still slightly warm, allowing it to drip a little down the sides. Scatter with the reserved walnuts before the icing sets.