Celery Root–Mushroom Latkes

Name: Celery Root–Mushroom Latkes
Ingredients: 1/2 cup sour cream; 2 tablespoons finely chopped fresh chives; 2 teaspoons white wine vinegar; Kosher salt; 1 russet or Yukon Gold potato (about 10 ounces), peeled; 1/2 medium celery root, peeled; 1 small onion; Freshly ground pepper; 1 large egg, beaten; 1/3 cup matzo meal or all-purpose flour; 1 cup halved and thinly sliced cremini mushrooms; 2 teaspoons fresh thyme, plus more for topping; 1 clove garlic, grated; Vegetable oil or rendered chicken fat, for frying