Prepare asparagus stem pesto according to the recipe and set aside. Bring 6 quarts of salted water to a boil and cook the pasta until the desired degree of doneness (about 7-10 minutes). Drain pasta and set aside.
Cut the asparagus in half lengthwise and into 1" pieces. Cut the cauliflower into bite-sized pieces, including stems. Prepare the rest of the vegetables.In a sauté pan heat the canola oil over high heat. Add the cauliflower and sear on all sides. Add the mushrooms and brown. Add the asparagus spears and garlic cloves and sauté for 3-5 minutes. Do not burn garlic. Add the asparagus pesto and fettuccini. Mix well to coat the ingredients and to warm the pasta through. Season with salt and pepper.
Divide the pasta mixture evenly between dishes. Drizzle the lemon juice over the top and garnish with shaved Parmesan and pine nuts.