Grilled Goat Cheese Burger with Onion Jam and Toasted Walnuts

For the onion jam, peel and thinly slice or grate the onion.

Sauté it in a little oil, season with salt and sugar, add the vinegar and star anise, then cook until jam-like.

For the vinaigrette, mix the mustard and 0.5 dl olive oil with an immersion blender, and season with a pinch of salt and sugar, or a spoonful of honey.