On a flat surface, butterfly the two chicken breasts into 4 thinner pieces. Pat dry with a paper towel and season with salt and pepper on both sides.
Grate the garlic, chop the shallot or onion, trim the ends of the asparagus and chop them into 1-inch pieces. Set the board aside and have the ingredients ready.
Cook the Pasta:
Bring a large pot of water to a boil and cook penne pasta according to package directions. During the last 5 minutes of cooking, add the chopped asparagus to the pasta. Cook them with the pasta for about 5 minutes. Once cooked, reserve ½ cup of pasta water, drain, and set aside.
Time to cook in the pan:
Heat a large pan over medium-high heat. Once hot, add the oil, heat it up, and spread it around the pan to coat.
Place the chicken breasts in the hot pan and cook, without moving them, for 4 minutes on the first side, then once golden and seared, flip them over and continue cooking for an additional 4 to 5 minutes until the chicken breasts’ internal temperature reaches 165F. Remove from pan onto a plate or cutting board.
To the same pan, add the butter and melt it; add the chopped shallot or onions and sauté for about 2 minutes, until the onions are soft and translucent. Add the garlic, and stir to cook the garlic for about 30 seconds.
Add the chicken broth and milk or half and half to the pan, bringing it to a simmer while stirring the tidbits from the bottom of the pan. Add the thyme, stir to combine, reduce the heat to medium-low, cover the pan with a lid, and simmer the sauce for 10 minutes.
When the sauce is ready, slice the chicken breasts diagonally into ½-inch strips and add them to the pan with the juices from the board.
Transfer the drained pasta and asparagus to the pan with the chicken and sauce. Add the parmesan cheese, and squeeze ½ of the lemon into the pan. Toss everything to combine and slowly add the pasta water to thin out the sauce while tossing it around.
Serve:
Plate the chicken asparagus pasta and sprinkle with parmesan cheese. Squeeze a lemon wedge over each plate for extra zest.