Preheat oven to 350 degrees.
Cook pasta in large pot according to package directions. While pasta is cooking, toast pine nuts on cookie sheet in preheated oven for 5 to 7 minutes. Set aside.
Melt butter in large skillet over medium heat. Add shallots or leeks and cook for 5 minutes, stirring occasionally. Add garlic; cook 3 more minutes, stirring occasionally. Add broth, salt and pepper; simmer uncovered for 5 minutes.
Discard stems from spinach; tear any large leaves in half. Drain pasta and return to pot. Add spinach; toss well. (Spinach will wilt slightly.) Add butter mixture; toss again. Transfer to two warmed serving plates and sprinkle with pine nuts. Sprinkle with freshly grated cheese, if desired.