Step 1

Make the sauce. In a small bowl, stir together the mayonnaise, yogurt, sambal and parsley. If needed, loosen the sauce with a bit of water to make it drippy. Refrigerate until ready to use.

Step 2

Make the soup. Melt the butter in a medium pot over medium-high. Add the onions and celery and season with a pinch of salt and a few grinds of black pepper. Sauté until the vegetables are tender, but not browned, 5 to 7 minutes. Add the sauerkraut and garlic and cook while stirring to release the steam and moisture from the pot. Add the stock. Bring to a boil, then lower to a simmer over medium heat. Add the heavy cream and cook further until the liquid slightly reduces, 15 to 18 minutes. Use a blender or immersion blender to blitz the soup until smooth.

Step 3

Finish and serve. Preheat the broiler to low heat. Put 4 broiler-safe bowls (I use my French onion soup crocks) onto a sheet pan. Divide the corned beef and soup equally between the bowls, then top with croutons and cheese. Place on the top rack of the oven beneath the broiler and broil until the cheese melts and bubbles a bit, 2 to 3 minutes. Remove and serve with a drizzle of the chilled sauce.