Decide the vibe: nutty-browned (Gruyère), creamy-stretch (Fontina), mild-melty (Emmental/Monterey Jack), or quick-stretch (cheddar+mozzarella).
Use the 1:1 swap ratio for most dishes; for a blend, start with 1:1 total cheese by weight (cheddar + mozzarella combined).
For best browning, shred or grate the cheese so the surface melts and caramelizes faster.
If the substitute tastes flatter than raclette, add 1–2 small pinches of salt or mustard powder to lift the flavor before serving.
Taste after melting: if it’s too mild, swap part of it for a sharper cheese (a little more cheddar); if it’s too sharp, add a small portion of mozzarella or a milder Swiss.