Remove and discard any bruised or tough outer leaves from the cabbage. Cut the cabbage in half through the stem, then carefully remove the dense core with a sharp knife. Place the cabbage cut side down on a board and slice as thinly as possible into fine shreds. (You can also use a mandoline or a food processor with the shredding attachment.) Transfer the cabbage to a large bowl.

Grate the carrots on a box grater, or cut into thin strips with a julienne peeler or food processor. Add to the bowl. Finely slice the red onion as thin as you can and add it to the mix. Sprinkle in the fresh herbs if you’re using them.

In a jug, whisk together the Dijon mustard, mayonnaise, yogurt, and white wine vinegar until smooth. Season with salt and pepper, then taste. If you prefer a sharper flavor, add a little more vinegar.

Pour the dressing over the vegetables and toss everything together with a large spoon until evenly coated. Finish with a sprinkle of paprika on top, then set aside until ready to serve.

Lightly butter both sides of each slice of sourdough bread. Spread a generous layer of mustard on one side of every slice.

On 4 slices of bread, pile on the slaw. Layer the corned beef evenly over the slaw, then top with slices of cheese. Place the remaining slices of bread on top, mustard side down, to make sandwiches.

Heat a large non-stick frying pan over medium-high heat. Add a little butter, then cook the sandwiches until golden and crisp on both sides, and the cheese has melted.

Remove from the pan, slice each sandwich in half, and serve warm.