Preheat the oven to 160°C.
Dry-fry the walnuts in a pan, let them cool, then roughly chop.
Heat the butter and sugar in a saucepan. When the sugar is melted, take the pan off the heat, add the honey and let it cool.
Beat the eggs slightly and add to the cooled sugar & butter.
Mix the flour with the nuts, then combine with the egg-butter mixture.
Grease and line a 20 cm square baking tray with baking paper and pour in the batter, spreading it out evenly.
Bake for about 30 minutes, until golden and an inserted skewer comes out clean. Turn it onto a wire rack and let it cool.
Cut into squares or slices - dust with powdered sugar, if you like.