For the broccoli rabe pesto: Fill a large pot with water, add a pinch of salt and bring to a boil; prepare a bowl of ice water. Add the broccoli rabe to the boiling water and cook until bright green, 3 to 4 minutes. Plunge the broccoli rabe into the bowl of ice water and leave it to cool completely for 5 minutes. Save the hot boiling water for cooking the pasta later.
Remove the broccoli rabe from the ice water, squeeze out excess water and drain well on a kitchen towel-lined plate. Transfer it to a food processor and add the parsley, pine nuts, lemon juice, garlic and salt and pepper to taste. Put on the lid and start pureeing the mixture while slowly drizzling in the olive oil. Transfer the pesto to a bowl and stir in the Parmesan.
For the pasta: Bring the broccoli rabe water back to a boil. Cook the pasta in the boiling water according to the package instructions.
While the pasta cooks, heat 2 tablespoons olive oil in a 12-inch pan over medium heat. Add the sausage and cook until brown, 6 to 7 minutes. Deglaze the pan with 1/4 cup of the pasta water.
Add the remaining 2 tablespoons olive oil to an 8-inch saute pan and allow it to get hot over medium heat. Add the fresh breadcrumbs and cook until golden brown and crispy, 4 to 5 minutes; set aside.
Reserve about 3/4 cup of the starchy pasta cooking water, then drain the pasta and put it back in the same pot. Add the sausage, pesto and a touch of the starchy water to loosen it. Toss well to make sure the pasta is well coated and transfer it to a serving platter. Scatter the golden crispy breadcrumbs all over the top. Garnish with more toasted pine nuts and Parmesan as desired.
The pesto can be made a few hours in advance. Just cover with plastic wrap and pop it in the fridge until ready to use.