Cook the pasta according to the instructions on the box
Add pine nuts to a large, dry skillet. Toast over medium-low heat until golden brown, tossing occasionally. Watch carefully, as pine nuts will burn quickly. Remove and set aside.
Melt butter in large skillet. Add onion and lightly season with salt. Cook over medium-low heat for about 5 minutes, until onions are golden. Remove and set aside in small bowl. Add 1/2 tablespoon oil and sliced garlic, and cook until golden on both sides. Remove, and add to bowl of onions.
If using Italian sausage, wipe pan clean. If using turkey or chicken sausage, add 1/2 tablespoon oil
Break up sausage into small pieces, and brown sausage in pan over medium heat.
Add red pepper flakes when sausage is almost browned through. Add kale and broth to pan. Reduce heat to low, and cook until kale is tender. The smaller the pieces of kale, the faster they will cook.
Drain the pasta, reserving 1 Tablespoon of pasta water. Add the pasta, reserved water, spinach, garlic and onions. Cook until water is absorbed and spinach has wilted
Add pine nuts and black pepper, and stir to combine
Transfer to a serving bowl. Top with freshly grated parmesan cheese. You may also want to add a few more red pepper flakes