Make the dressing: In a medium bowl, whisk together the mayonnaise, ketchup, pickle, horseradish, Worcestershire sauce and garlic powder. Thin with a little water if needed for a drizzling consistency. Taste and season with salt and pepper. (Yield: scant ½ cup. You can make the dressing up to 2 days ahead. Keep covered in the fridge. Whisk before using.)
Melt the butter in a large skillet over medium-high heat. Add the cole slaw mix, season with salt and pepper and cook, stirring, until tender, 4 to 6 minutes. Add the turkey and cook, tossing, until just warmed, 1 to 2 minutes longer. Remove from the heat; let cool slightly.
Add the sauerkraut and swiss cheese; toss to combine. Divide between 2 bowls, drizzle with dressing (you may not use all of it), top with crushed crackers, if using, and serve.