Heat the oven to 180°C/gas 4. Line a 25 cm by 12 cm loaf tin with baking paper. Blitz the walnuts in a food processor until finely chopped.
Melt the butter, sugar and honey in a medium pan over a gentle heat. When melted and blended, remove from the heat and stir in the walnuts. Whisk together the eggs and milk and add to the walnut mix, then add the flour and baking powder and blend until smooth. Pour into the prepared loaf tin and bake for 30 minutes, then reduce the heat to 150°C/gas 2 and bake for a further 30 minutes. Cool for 10 minutes, remove from the tin and dust with icing sugar. Best eaten at least 24 hours later – just wrap in tin foil when cool.