Prepare a large bowl of salted ice water. Bring a large pot of salted water to a boil. Add the asparagus and garlic and cook until the asparagus is crisp-tender, about 2 minutes. Transfer the asparagus and garlic to the ice water using a slotted spoon (reserve the pot of water). Let the asparagus and garlic cool, then drain and pat dry. Chop off the asparagus tips and set aside; roughly chop the stems.
Make the pesto: Toast the hazelnuts in a large dry skillet over medium-high heat, about 5 minutes. Transfer to a food processor and let cool, then pulse until roughly chopped. Add the asparagus stems and garlic to the food processor; pulse until smooth. Add the basil and chervil. With the motor running, slowly add the olive oil and puree until smooth. Add the truffle pecorino, parmesan, lemon zest and juice, 1 teaspoon salt and a few grinds of pepper, pulsing until combined.
Return the pot of water to a boil. Add the pasta and cook as the label directs. Reserve 3/4 cup cooking water, then drain the pasta and return to the pot. Add the pesto, butter and the reserved asparagus tips. Cook over low heat, tossing and adding the reserved cooking water as needed to loosen, until coated. Season with salt and pepper. Drizzle each serving with olive oil and top with more truffle pecorino.