Decide what role vacherin plays in your recipe: creamy melt, briny tang, or scoopable spread.
Use the listed ratio from the substitute options, then break or shred the cheese so it disperses evenly.
If your substitute is creamier than vacherin, warm it briefly or stir in a small splash of milk/cream to smooth.
If your substitute is less tangy (like Monterey Jack), add a tiny tang adjuster (lemon juice or a spoon of yogurt) and taste.
Bake or heat until just melted; avoid long high-heat simmering to prevent graininess or separation.