Divide ground turkey into four ¼ pound patties – sized appropriately for the bread you’re using. Season turkey patties to taste with S& P, and cook in a skillet with a little melted butter over medium heat until cooked through (internal temperature should be 160-165°F). Remove from heat and cover to keep warm.
Carefully wipe the skillet clean, and return to medium heat.
Butter one side of each slice of bread and place into a heated skillet - buttered side down - to toast.
Once toasted, flip bread over so toasted sides are up.
Add 1 Tbsp (or more, to taste) sauce to each slice, then Swiss cheese, sauerkraut, and pastrami. Then place 1 – 2 turkey burger(s) and/or slices of pastrami on top with the second slice of toast. Warm for 2 – 3 minutes per side, and enjoy immediately.