If you can find it, spear-shaped Treviso radicchio is the best choice for this recipe (but round Chioggia works, too). The wilted radicchio and spinach leaves perfectly complement the spicy red pepper flakes and salty bacon.
garlic (about 12 to 14 cloves)
olive oil (divided)
bacon (about 8 slices) (cut crosswise into 1/2-inch-wide strips)
onion (chopped, about 2 cups)
low-salt chicken broth
(packed) Treviso or Chioggia radicchio leaves, (coarsely torn, from about 2 medium heads)
(packed) Earthbound Farm Organic Baby Spinach (about 10 ounces) (torn in half)
freshly grated Parmesan cheese (plus more for serving)
dried crushed red pepper flakes
Salf and freshly ground black pepper to taste
Preheat oven to 375 degrees F. Cut off the top 1/2 inch of the garlic head, exposing the cloves. Place the garlic, cut side up, on a sheet of foil and drizzle with 1/2 teaspoon olive oil. Wrap the garlic in foil and roast until soft, about 40 minutes. Let stand until cool enough to handle. Squeeze the soft garlic into a small bowl.
Cook the pasta in a large pot of boiling, salted water until al dente (just tender but firm to bite), stirring occasionally.
Meanwhile, cook the bacon and onion in a large, heavy skillet over medium-high heat until golden brown, stirring occasionally, about 12 minutes. Add chicken broth, remaining 5-1/2 teaspoons olive oil, and roasted garlic. Bring the mixture to a simmer, stirring occasionally. Add radicchio, spinach, and basil; stir to combine. Simmer just until the radicchio and spinach wilt, about 1 minute.
Drain the pasta and return to the same pot. Add the radicchio-spinach mixture to the pasta. Add 1 cup grated parmesan and crushed red pepper; toss to coat. Season to taste with salt and pepper. Serve with additional parmesan cheese alongside.