To poach turkey, in large saucepan, place breast, onion, carrot, celery, garlic, thyme, lemon, salt, and peppercorns. Add enough water to completely cover turkey by at least 1 inch. Bring water to a very slight simmer with just a few bubbles breaking the surface and cook, partially covered, for 20 minutes, or until meat is cooked through and an instant-read thermometer inserted into the thickest part of the meat registers 165 F. Adjust heat as needed during cooking to maintain the slight simmer (you don’t want to boil the meat). Skim off any foam that forms on surface of water.

To make gravy, in medium-sized saucepan over medium heat, melt butter. Add mushrooms, shallots, garlic, and salt; cook until mushrooms have softened, about 5 minutes. Add wine, raise heat to medium-high, and boil until liquid has reduced by half, about 3 minutes.

In small bowl, whisk cornstarch, 1 Tbsp at a time, into 1/2 cup of the broth. To gravy pan, add remaining broth, thyme, and pepper. Return to a boil and then stir in cornstarch-broth mixture and cranberries. Simmer until thickened, 6 to 8 minutes.

Slice turkey and place on serving platter. Serve with sauce boat of gravy alongside.