Slow Cooker White-Bean Parmesan Soup

dry cannellini beans, soaked overnight and drained

Kosher salt and black pepper

Parmigiano-Reggiano, hard rinds cut off and reserved

wheat berries

olive oil

large onion, finely chopped

fennel bulb, cored and finely chopped, fronds roughly chopped and reserved

celery stalks, sliced 1/2-inch thick

garlic cloves, roughly chopped

fennel seeds

red-pepper flakes

sprigs fresh rosemary

dry white wine

chicken stock or broth

Leaves from 1 small bunch flat-leaf parsley, chopped

Juice of 1 large lemon