Mix the mayonnaise, pickle, ketchup and hot sauce in a small bowl. Mix the coriander, smoked paprika, allspice, mustard, 1/2 teaspoon salt and 1/2 teaspoon pepper in a shallow dish. Roll the beets in the spice mixture to coat. Slice the beets 1/4 inch thick.

Spread each slice of bread with the mayonnaise mixture. Lay 1 cheese slice on each of 2 slices of the bread. Top with the sauerkraut. Divide the sliced beets and arrange on top of the sauerkraut. Top with the remaining cheese. Close the sandwiches, mayonnaise-side down. Press lightly with your hand.

Heat a large skillet over medium-low heat. Add 1 tablespoon of the butter. When the butter is melted, add the sandwiches. Cook until golden on the underside, about 3 minutes. Add the remaining tablespoon butter, let melt, then flip the sandwiches. Cook until the underside is golden and the cheese is melted, about 3 minutes more. Cut the sandwiches in half before serving.