Dice 1 fennel bulb. Heat 40ml olive oil in a saucepan over medium-high heat, add diced fennel, carrot, celery, onion and garlic, and stir occasionally until softened but not coloured (5-6 minutes).
Add lentils, stock, thyme sprigs and bay leaves, and 150ml water, bring to the simmer and cook until lentils are tender, and liquid has almost completely evaporated (15-20 minutes).
Drain off any remaining liquid, season to taste and set aside to cool (discard thyme sprigs and bay leaves).
Combine hazelnut oil, vinegar, lemon juice and remaining olive oil in a screw-top jar and shake to emulsify. Season to taste.
Thinly shave remaining fennel bulb on a mandolin and combine in a bowl with lentils, radicchio, parsley, hazelnuts, thyme leaves and reserved fronds.
Add vinaigrette, season to taste and toss to dress well. Scatter goat’s cheese on top and serve.
