Method

Start by melting the butter over a low to medium heat.

Add the flour and cook until it forms a blonde roux.

Add half the milk and whisk until smooth and any lumps have been removed. Add the remaining milk and whisk to combine. Stir continuously until thickened.

Add 30g of the Parmigiano Reggiano, all of the cheddar and half of the freshly grated truffle.

Transfer to a shallow container. Cover with baking paper, ensuring the paper is touching the béchamel, and chill.

Preheat the oven to 200°C.

Once the béchamel has cooled, cut the sourdough across into 1.5cm slices. Pro tip: match your slices so the béchamel does not ooze out during toasting.

Lay the bread out in pairs. Spread butter over the outside of each slice, then sprinkle with the remaining grated Parmigiano Reggiano. Stack the pairs with the buttered and parmesan-coated sides together.

Spread the béchamel evenly over the unbuttered inside surfaces of the four toasties. Divide the Gruyère between the toasties and sprinkle it over the béchamel.

Place the top slices over the béchamel and cheese mixture, keeping the buttered and parmesan-coated sides facing out.

Preheat a non-stick pan over medium heat and lightly spray it with oil. Alternatively, use a small amount of olive oil.

Cook the toasties until lightly golden, then flip. Transfer them to the oven for seven minutes, or until crisp and golden.

Remove from the oven and cut into fingers—or devour them however you like.

For extra decadence, finish with additional grated Parmigiano Reggiano and fresh truffle.