Grilled cheese is a near-perfect food on its own, but adding bacon, kimchi or, in this case, heaps of caramelized onions really makes it special. Caramelizing onions takes a good half-hour, so save this recipe for when you have a little extra time and company (this recipe serves two). If time permits, you could even prep them ahead in a slow cooker. Rather than layer the grated Gruyère and the warm caramelized onions in the sandwich, you should stir them together before assembling, which…
