In a large skillet, heat the oil, over medium-low to medium. Add the onions, garlic, and sugar; seasoned with the salt, black pepper, white pepper, and thyme. Cook, stirring occasionally, until the onions are caramel in color, about 20 minutes. Stir in ¼ cup water and stir to evaporate, 1 to 2 minutes. Remove heat and stir in the sour cream.
Meanwhile, for the sandwiches, in a small pot, warm the sauerkraut and the caraway and cumin seeds over low heat until just heated through, about 5 minutes.
After the onions have cooked for about 15 minutes, heat griddle or grill over medium. Lightly butter one side of each break slice and build sandwiches by layering the mustard, half of the cheese, a little sauerkraut, the turkey, onion dip, and then the remaining cheese between the bread slices (buttered sides out). Cook until the bread is golden and the cheese melts, about 2 minutes per side. Cut in half. Serve with pickles and chips.
From Rachael Ray Every Day.