How to Make It
In a large heavy cast iron or non-stick skillet, heat 1 tablespoon of the butter over medium low heat until melted. Fry half of the English muffins, cut side down, until golden, about 3 minutes. Repeat with 1 more tablespoon butter and the remaining English muffins.
In a medium bowl, stir together the cheeses, mayonnaise, scallion and a large pinch each salt and pepper. Divide the cheese mixture between the English muffins, pressing the tops down to make sandwiches.
Heat the remaining 1 tablespoon of butter in the skillet over low heat until melted, then place the sandwiches in the skillet and cover. Cook, turning occasionally, until the cheese is melted and the English muffins are toasted, 4 to 6 minutes total. Serve.