Spread a thin, even layer of softened butter on the outside of both slices.
Then layer the gouda between the bread pieces, buttered sides facing out.

Heat a skillet over medium-low to medium heat. Grill the sandwich slowly until the bread is golden brown, flip and continue grilling until the cheese is melty. Remove from heat and enjoy.

If you are packing this sandwich for later, let it cool before slicing it in half and packing it in a hard lunch container. Pack any sides like fruit or veggies in separate compartments. Use an ice pack if needed.