Finely dice the carrots, celery, onion and fennel. This can be done by hand, or in a food processor.
Add olive oil to a large dutch oven or pot, and heat over medium heat.
Add carrots, celery, onion, and fennel to the pot, and season with salt and pepper to taste.
Stir to combine, then cook, stirring occasionally for 5-7 minutes.
Add garlic and tomato paste, and stir well. Cook 2-3 minutes, until tomato paste begins to darken a bit.
Add the lamb to the pot and cook, breaking up as you go, for 5-6 minutes, until fully browned.
Add the red pepper flakes, dried basil, bay leaves, wine, crushed tomatoes and parmesan rind (if using).
Stir well, reduce heat to low, cover, and simmer for 1 hour. If using a parmesan rind, check on it periodically to make sure it doesn’t stick.
After 1 hour, remove the bay leaves and parmesan rind, and stir in the butter until melted and fully incorporated.
Serve with pasta, parmesan cheese, and fresh basil or fennel fronds (for garnish).