Make Pasta. Add pasta to a large pot of salted water and make al dente pasta according to package instructions. Add broccolini to cook for 2-3 minutes before it's time to drain the pasta. Before you drain the pasta, remove at least 2 cups of the pasta water Drain. Set aside.
Make sausage. Let sausage cook in a large skillet or frying pan over medium heat. Add onion, garlic, capers, salt, fennel, chili flakes and lemon zest. Cook until onions are translucent, 3-5 minutes, adjusting heat if necessary. Taste and add more salt to taste.
Combine. Add cooked pasta to the sausage mixture and toss in reserved pasta water, butter, lemon juice over medium heat. Add parmesan. Toss. If you feel like the pasta needs a little more liquid, you can always add a splash of water, veggie or chicken broth. If it feels like there is a lot of liquid, no worries. The pasta will absorb and you'll end up with slightly saucier noodles. It's hard to go wrong here.
Toss in herbs. Taste and adjust salt and lemon juice to taste. Grate more parmesan over the top of the pasta and garnish with more basil leaves. Optionally, give the pasta a generous sprinkle of ground, fermented black garlic; I've been adding 1 teaspoon to an adult-sized dinner portion and it is to die for.