Put the mince in a large bowl with the breadcrumbs, onion, parsley, dill, ½ tsp salt and a generous grind of black pepper. Mix to combine, then shape into about 30 golf-ball-sized balls.
Trim the fennel, discarding the stalks but reserving the fronds for garnish. Cut each bulb in half lengthways, then cut into 2cm-wide wedges.
Heat a heavy bottomed casserole dish over medium heat. Fry the meatballs in 2 batches with a drizzle of avocado oil, turning regularly, for 5 minutes or until browned all over. Transfer to a plate and set aside.
In the same pan, add some more avocado oil and saute the fennel wedges for 3 minutes or until browned all over. Add the white wine then once it’s bubbling, stir in the tomatoes, lemon and season well. Once the mix has come to a boil, lower the heat to low, cover the pan and leave to simmer gently for 10 minutes, until the fennel starts to soften.
Stir in the meatballs to the pan and place in the oven for 30 minutes.
Garnish with the pine nuts and reserved fennel fronds.