Place morels in a sieve and rinse with water. Place them on a clean kitchen towel and dry thoroughly. Cut large morels in half and keep smaller ones intact. Trim off any woody ends.
Boil water, and add 1 tbsp salt. Cook pasta until al dente. Reserve 1 cup of pasta water.
In a large pan or Dutch oven, heat olive oil and chili flakes over medium-high heat. Add onion and cook until translucent. Add garlic and broccolini. Add a splash of pasta water to get things moving and to help steam the tougher stems. Cook for several minutes.
Add in asparagus. Season with salt and pepper. Add in mushrooms and toss to combine. Cook for 2-3 minutes until morels start to soften. Add in half of the butter. Toss in pasta and lightly toss into the veggies. Add in the remaining butter, the lemon juice, and a splash of pasta water to emulsify. Grate cheese and toss again. Check for seasoning and serve immediately.