Use 1 tbsp butter to butter the slices of bread with butter on one side.
Warm the olive oil and remaining 1 tbsp butter in a large pan over a low heat.
Add the garlic, onions, cayenne and black pepper.
Sweat for about 5 minutes until the colour deepens and you have a paste.
Turn up the heat, add the mushrooms in a single layer.
Fry for 2-3 minutes until just beginning to brown on both sides – turn carefully to keep the slices whole. Taste and add a little salt, if needed – if the butter is salty, you might not need any. Tip into a bowl and set aside.
Place half of the slices of bread in the pan, butter side down. Use half the Jarlsberg® cheese to top each slice of bread.
Layer the mushrooms on top and sprinkle the coriander, if using.
Layer on the remaining Jarlsberg® cheese.
Top each toastie with the remaining slices of bread, butter side up. Put a lid on the pan to help the heat to reach the cheese.
Flip the toasties when they’re golden underneath and replace the lid again.
When the bread is golden on both sides and the Jarlsberg® cheese is melted, remove from the pan, cut in half and serve.
For an extra treat, try adding a spoonful of caramelised onion to each toastie.