Remove any unpopped popcorn kernels. Put the popcorn in a food processor; cover and pulse until coarsely ground. Place the popcorn in a shallow dish and add thyme, salt, and pepper.
Place the egg in another shallow dish; add 1 tablespoon water and beat lightly with a fork. Place flour in another shallow dish.
Dredge the chicken in the flour to coat, shaking off excess. Dip the chicken in the egg mixture, then in the popcorn mixture to coat.
Put the butter and oil in a large skillet over medium-high heat. Add chicken and cook 10 to 12 minutes or until chicken is cooked through (170°), turning occasionally to brown evenly. Reduce to medium heat if necessary. Serve with lemon wedges.