The secret to this roast beef sandwich is the Jarlsberg cheese (it's so good 🤤) and tons of caramelized onion jam! Caramelized Onion Jam Recipe This sweet and savory onion jam is the perfect addition to burgers, sandwiches, cheese boards, and more! It’s rich, deeply caramelized, and packed with flavor. Ingredients: 4 large onions (yellow, red, or a mix), thinly sliced 2 tbsp butter or olive oil ¼ cup brown sugar ⅓ cup balsamic vinegar (or apple cider vinegar for a milder tang) ¼ cup water 1 tbs