1. In a small bowl, stir the blackberry jam together with the balsamic vinegar until fully combined. This simple step brings out the deep, complex flavors that make this sandwich special.
2. Lay out your slices of sourdough bread on a clean surface. Spread a thin layer of the blackberry-balsamic mixture evenly onto two of the slices. This will be the sweet, tangy foundation.
3. Arrange the sharp white cheddar slices over the jam-spread bread. If you’re adding basil leaves or thinly sliced red onion, layer them on top of the cheese now for a fresh, aromatic lift.
4. Top with the remaining slices of bread to form two sandwiches.
5. Spread softened butter generously on the outside of each sandwich. This will help achieve that golden, crispy crust—not unlike the golden edges of Mama Lu’s biscuits fresh from the oven.
6. Heat a heavy skillet or cast iron pan over medium heat. Place the sandwiches in the pan and cook for about 3-4 minutes on each side, pressing gently with a spatula, until the bread is toasted golden brown and the cheese is melted through.
7. Flip carefully and watch for that perfect melt. The smell alone will bring you back to those kitchen moments with Mama Lu, where the warmth of the stove was always the heart of the home.
8. Once both sides are golden and the cheese is oozy, remove from heat. Let the sandwich rest for a minute before slicing — this keeps the filling from running everywhere and lets the flavors settle.

One tip I’ve learned from years of cooking with Mama Lu is to trust your instincts—if your skillet gets hot too fast, lower the heat and be patient. A slow, steady toast is what gives you that perfect crunch without burning the bread.