Bring a large pot of salted water to a boil. Blanch the broccoli rabe until just tender, about 90 seconds, and immediately transfer to the ice bath until cooled. Drain water and squeeze out excess liquid, then place in the carafe of a food processor. Add the basil, pistachios, grated Parmesan and smashed garlic. Pulse with olive oil until still chunky but all ingredients have combined, using just enough olive oil to loosen. Add the mascarpone and pulse until just combined into the pesto. Remove the pesto from the carafe and set aside.
Heat a medium skillet over medium heat. Add olive oil to just barely coat the skillet. Sear the sausages on all sides until cooked through and beginning to brown, about 12 minutes. Remove from the heat and set aside.
Whisk together the red wine vinegar, minced garlic and 1/4 cup olive oil in a small bowl. Season with salt and crushed red pepper.
Toss the arugula, endive and escarole together in a bowl with the vinaigrette. Spoon all but a few spoonfuls of the pesto on the bottom of a plate or serving dish. Top with the dressed greens, mozzarella, sausages sliced on a bias and more of the pesto. Serve!