Created by Julie Van Rosendaal
Put the oil and butter into a skillet set over medium heat and cook the onions with the thyme and a pinch of salt for 8-10 minutes, stirring often, until deep golden.
Assemble sandwiches with two slices of cheese and some caramelized onions in between, spreading the outside of the bread with soft butter or mayonnaise. Return to the skillet and cook for 5-8 minutes, flipping as necessary until the bread is crisp and golden and the cheese has melted. (Alternatively, bake them in the oven at 425˚F for 10-12 minutes, flipping halfway through.)