Roast one head of garlic ahead of time. Cut top off bulb, drizzle top with olive oil, submerge bottom half of bulb in bowl of water, roast in microwave for 7-8 minutes, until soft enough to squeeze cloves from bulb, let cool. Set aside.
Caramelize onions by sautéing in skillet with 3 teaspoons olive oil. Add 1 tablespoon balsamic vinegar to finish caramelization. Set aside.
Cook pasta al dente per instructions, reserving ¾ cup of the starchy pasta water before draining. Drain remaining pasta water. Return cooked noodles to dry pot, toss with a drizzle of olive oil to prevent sticking. Set aside.
spoon to break up roasted garlic cloves; they will diffuse and sort of melt into the oil as they cook. Sauté the mixture until apples are fork tender, about 15 minutes. Sprinkle with 2 tablespoons balsamic vinegar.
Add cooked pasta to 12-inch sauté pan with apple mixture and toss well. Add reserved pasta water and toss well over medium heat. Sauté for another five minutes until water absorbs. Add baby spinach and pecan crumble during last minute of cooking.
Turn off burner and stir in minced sage. Taste and adjust flavors as needed.
Serve the pasta hot with desired garnishes (shown with more fresh sage, Parmesan cheese and ground pepper).