For the walnut nibbles, chop the rosemary needles very finely.
Mix the walnut oil, rosemary, lemon pepper and cardamom in a bowl. Mix in the walnuts so they are well coated with the spice oil.
Line a baking sheet with parchment paper and spread the nuts evenly on it.
Bake the marinated walnuts in the already preheated oven at 160 °C for about 25 minutes.
Put the walnut nibbles in a tin, store in a dry place and consume as soon as possible.