This may look like a traditional Reuben, but it’s fancy roast beef with horseradish sauce in disguise.
In a small bowl, mix the sour cream, dill, chives, ketchup, relish and beet horseradish. Season the dressing with salt and pepper.
Butter one side of each slice of the bread and heat a griddle pan over medium.
With the buttered side facing down, top 4 slices of the bread with some of the dressing and 2 slices each of the smoked Gouda.
In a small saucepan, heat the sauerkraut with the seeds over medium just to heat through, about 5 minutes.
Top the Gouda with the roast beef and sauerkraut, then the Jarlsberg. Top with the remaining bread, buttered side up. Griddle until the cheeses melt and the bread is deep golden and crispy, about 5 minutes per side. Cut the sandwiches from corner to corner and serve with the pickles.