Slice the mushrooms and Swiss cheese into even pieces. Gather your chosen bread and butter.

Heat a skillet over medium-high heat and add a splash of olive oil or a pat of butter. Sauté sliced mushrooms for 5-7 minutes until golden brown.

Butter one side of each slice of bread. Toast the buttered sides of the bread in the same skillet for 2-3 minutes until golden and crispy.

Layer sautéed mushrooms on one slice of toasted bread, followed by Swiss cheese. Top with another slice of bread, buttered side out.

Cook the assembled sandwich in the skillet for 3-4 minutes per side, pressing down gently until golden brown and cheese is melted.

Remove the sandwich and let it cool for a minute before slicing. Serve warm.