Heat your pan on medium low heat.
Spread 1/2 tbsp of mayo on one side of each bread slice and 1/2 tbsp of soften butter on the opposite side.
Place one slice of bread, mayo side down in the hot pan.
Layer the bread with one slice of gouda and 2 slices of cheddar, and then top it with your other bread slice, mayo side out.
Cover and cook for 2-3 minutes until golden brown, then flip and cook for another 1-2 minutes.
Repeat the steps for your remaining sandwich.
Slice in half and serve hot on its own or pair it with a bowl of creamy tomato soup.