Meanwhile, cook the bacon in a non-stick skillet over medium heat until browned and crisp. Drain on paper towels and finely chop; set aside. Drain all but 1 tablespoon of bacon fat from the skillet and return to medium heat and add the butter. Add the onion and sauté for 5 minutes. Add the apple, brown sugar, vinegar, salt, pepper, and thyme and cook, stirring occasionally, until golden brown, about 10 minutes. Remove from the heat, transfer the mixture to a medium bowl, and cool completely. Once cooled, add the cheese, crème fraîche, egg, and cooked bacon, mixing until combined.