Heat a nonstick skillet over medium heat. Spread plenty of soft butter on the outside of both pieces of bread. Drop one slice butter side down into the hot skillet. (If your stove runs hot, start at medium-low.) Cover the slice of bread with half of the shredded cheese. Spread the vegetables across the cheese layer and top with the remaining cheese and the second slice of bread, butter side up.

Cover the pan with a lid - this is important, so don't skip this part. Let the sandwich cook undisturbed for at least a minute. Uncover and check to see if the bottom slice of bread has browned. Let cook until golden brown, usually about 3 minutes on medium heat.

Press down slightly on the top slice to help the cheese stick to both slices. Use a thin spatula to carefully flip the sandwich over. COVER WITH A LID once more.

If your cheeses aren’t melting as quickly or smoothly as you’d like (especially if you are using pre-shredded cheeses) add one teaspoon of water to the edge of the pan and quickly cover with the lid. This helps steam the cheese and even pre-shredded cheeses will melt beautifully.

Check to see if the second slice of bread is golden brown. It should take about 3 minutes on medium heat. When it is ready, remove the sandwich to a plate and serve warm.