01 -
Warm a large non-stick skillet or griddle over medium heat until evenly heated, avoiding excessive heat.
02 -
Halve and pit the avocado, then scoop the flesh into a bowl and mash gently with a fork until creamy yet retaining some texture. Season with a pinch of sea salt and black pepper.
03 -
Toss mozzarella and sharp cheddar together in a bowl, ensuring an even blend for optimal melting.
04 -
Spread softened butter on one side of each bread slice. On the unbuttered sides of two slices, apply a thin layer of mayonnaise.
05 -
Place the mayonnaise-coated slices into the preheated skillet, mayonnaise side down. Evenly distribute the mashed avocado over each, then sprinkle with garlic powder and onion powder.
06 -
Generously mound the shredded cheese mixture atop the avocado. If using, arrange fresh basil leaves over the cheese layer.
07 -
Cover each with a remaining bread slice, buttered side facing upward. Grill for 3–4 minutes until the underside turns golden and crisp.
08 -
Carefully flip each sandwich with a spatula. Continue cooking for another 3–4 minutes until both sides are golden brown and all cheese has melted thoroughly.
09 -
Remove sandwiches from the skillet and allow to rest briefly. Slice diagonally and serve while hot, ensuring the cheese remains melty.