Melt 2 tablespoons butter in a large nonstick skillet over medium-high heat until lightly browned. Add pine nuts and sage; remove from heat. Remove from pan, and set aside.
Heat olive oil in pan over medium-high heat. Add garlic to pan, and sauté 30 seconds. Reduce heat to medium. Add 1 cup water and squash to pan. Cook for 12 minutes or until water is absorbed, stirring occasionally. Add remaining water, 1/2 cup at a time, stirring occasionally until each portion of water is absorbed before adding the next (about 15 minutes). Stir in sugar, salt, and pepper.
Cook pasta according to package directions, omitting salt and fat. Drain, reserving 1/2 cup pasta water. Combine pasta and squash mixture in a large bowl. Add reserved 1/2 cup pasta water, butter mixture, and 3/4 cup cheese; toss well. Sprinkle with remaining 1/4 cup cheese. Serve immediately.