- In a pot of salted boiling water, cook the asparagus for 2 minutes. Using a slotted spoon, remove the asparagus and chill in a bath of ice water. Drain. Cut in half lengthwise, then in half crosswise on an angle.
- In the same pot, cook the shrimp for 1 minute in the water. Using a slotted spoon, remove the shrimp and set aside on a plate.
- In the same pot, cook the pasta until very al dente, about 6 minutes (or 1 minute less than the cooking time indicated on the packaging).
- Meanwhile, in a skillet over medium-high heat, soften the shallot and garlic in the butter. Add the cream and thyme, if desired, and simmer for 5 minutes. Season with salt and pepper. Remove the thyme sprig.
- Reserve 1 cup (250 ml) of the pasta cooking water. Drain the pasta. Return the pasta to the pot.
- Add the cream mixture and reserved pasta cooking water to the pot. Toss to coat the pasta in the sauce and cook for 1 minute. Add the asparagus, shrimp, lemon zest and juice. Stir until everything is heated through. Adjust the seasoning. Serve immediately.