Prep Bread: Lay sourdough slices on a clean workstation. Spread softened salted butter evenly over the exterior face of all 8 bread slices.

Spread Condiments: Flip 4 slices over so butter is on bottom. Spread 1 to 1.5 tablespoons of sweet fig jam and a light dab of Dijon mustard across the unbuttered interior sides.

Layer Fillings: Place a layer of sliced sharp white cheddar over the fig spread. Top with thinly sliced Honeycrisp apples, a sprinkle of fresh thyme, baby arugula, and shredded Gruyere cheese. Cap each sandwich with remaining sourdough slices, buttered side facing outward.

Heat Skillet: Heat a large cast-iron skillet or griddle over medium-low heat. Do not rush high heat or bread will burn before cheese melts.

Grill Low & Slow: Place sandwiches into skillet. Cover loosely with an inverted lid or foil tent to trap steam for 3 to 4 minutes until bottoms are deeply golden brown and crispy.

Flip & Finish: Carefully flip sandwiches. Press down gently with a spatula and cook uncovered for another 3 to 4 minutes until bottom is golden and cheese is completely melted and bubbling.

Slice & Serve: Transfer to a cutting board, let rest for 1 minute, slice diagonally with a serrated knife, and serve immediately with that dramatic molten cheese pull!