Clean the radicchio and cut or pick into bite-sized pieces. Cut the fennel into wafer-thin slices (like onion rings).
Vinaigrette: Roast the coriander seeds in a pan without fat. Crush in a mortar (or grind in a blender) and stir in a small bowl with balsamic vinegar, olive oil, honey, salt and pepper.
Mix the radicchio and fennel, pour the marinade over them and garnish with chopped nuts and cheese shavings if desired.