Sweet Potato Sliders with Burger Sauce

First, preheat your oven to 400F (200C). Slice the sweet potatoes into rounds, about 1/4 to 1/2 inch thick. Arrange them on a baking sheet and bake for 30 minutes until tender. While the sweet potatoes are baking, prepare the burger patties. In a bowl, combine the lean ground beef with 1 egg, 1 tsp garlic powder, 1 tsp onion powder, 1 tsp chicken bouillon, 1/2 tsp salt, and 1/2 tsp pepper. Mix well and form into small patties, sized to fit the sweet potato slices. Cook the patties on a stovetop over medium heat until fully cooked through. For the burger sauce, whisk together 1/3 cup nonfat Greek yogurt, 2 tbsp sugar free ketchup, 1 tbsp relish, and 1 tsp mustard. To assemble the sliders, spread a dollop of burger sauce onto one sweet potato slice. Top with a cooked burger patty, a few arugula leaves, and a sprinkle of nonfat feta. Finish by topping with another sweet potato slice.