01 -
Spread softened butter on one side of each sourdough slice. Flip and apply a thin layer of mayonnaise to the opposite sides.
02 -
Combine shredded cheddar, Gruyère, blue cheese (if using), garlic powder, onion powder, thyme, smoked paprika, salt, and pepper in a bowl until seasonings are evenly incorporated.
03 -
Place two bread slices mayo-side up on work surface. Distribute cheese mixture evenly between them, then top with remaining slices, mayo-side down.
04 -
Heat a non-stick skillet or griddle over medium heat for 2-3 minutes until thoroughly warmed.
05 -
Transfer sandwiches to heated pan and cook for 3-4 minutes until bottom sides become golden brown and crispy, monitoring frequently to prevent burning.
06 -
Carefully flip sandwiches and grill for an additional 3-4 minutes, adding more butter if needed, until cheese completely melts and both sides achieve golden-brown perfection.
07 -
Remove from heat and let rest briefly. Cut each sandwich diagonally and serve warm, garnished with fresh arugula if desired.