In a large pot of boiling salted water, cook asparagus until bright green, about 2 minutes.
Add snap peas; cook 30 seconds.
With a slotted spoon or a small sieve, scoop out vegetables; transfer to a bowl.
Return water to a boil; add pasta and cook until al dente, according to package instructions.
Drain, reserving 1 cup pasta water; set pasta aside in colander.
In pasta pot, melt 2 Tbsp butter over medium heat.
Add asparagus, snap peas, and garlic; season with salt and pepper.
Cook, tossing, until vegetables are crisp-tender, about 2 minutes.
Add remaining 2 Tbsp butter, cooked pasta, avocado, herbs, cheese, and reserved pasta water.
Toss to combine; season with salt and pepper.
Serve topped with additional cheese, if desired.
-