Musselman’s Apple Butter creates delicious caramelized onions, taking boring grilled cheese to the next level.
Adjust oven rack to lower-middle position and heat oven to 350° F.
Heat oil in large skillet over medium heat. Add onions and sauté, until caramelized.
Stir in thyme, a generous sprinkling of salt and pepper, and the apple butter. Cook to heat through.
Set bun bottoms and tops on a sheet pan (cut side up). Bake 5 minutes just to toast the buns slightly.
Top each bottom bun with a slice of cheese, then a Tablespoon of the cooked onion.
Spread each bun top with a teaspoon of mustard and cap each sandwich.
Bake sliders until cheese melts, 5 to 7 minutes. Serve.