My mom makes these for my kids as an afternoon snack. It's a nice alternative to sweets. Be brave with the mayonnaise -- you need a lot. Go easy on the paprika. Or just skip it. The most exciting part of these toasts is biting through the hot melted cheese and BAM there's this comforting and warm layer of mayonnaise. It's very much like melted butter. But better. —Phyllis Grant
Cut the baguette in thirds, then cut each third in half. Place each half cut side-up on a sheet pan. Broil (but not too close to the flame) until the bread is crispy and lightly browned.
Spread each piece of bread with as much mayonnaise as you dare. Cover mayonnaise with slices of cheese. Sprinkle cheese with a very thin layer of paprika. Broil until cheese is melted and browning. Don't panic. The paprika gets almost black under the broiler. That's okay. Eat a piece as soon as you can pick it up.