Prepare the Maple-Mustard Sauce by whisking all the ingredients together in a small bowl until smooth. Store in an airtight container in the refrigerator for up to 1 week.
Prepare the sweet potatoes by preheating the oven to 400°. Scrub the sweet potatos, then use a knife to cut thin slices that are ¼"- ½" thick. In a large bowl, toss the slices with the coconut oil. Spread the slices out on a baking sheet. Bake for 30-40 minutes (flipping halfway), until the slices are lightly browned.
Preheat the panini press.
To assemble the sandwiches, lay the slices of bread out on a cutting board. Spread the Maple-Mustard Sauce on each slice of bread. Layer the spinach over 4 of the slices of bread. Next add the sweet potato, then apple slices. Spread a little more Maple-Mustard Sauce over the apple slices. Next, layer the avocado, sauerkraut and vegan cheese. Top with the other slices of bread.
Gently transfer the sandwiches to the panini press. Grill until the cheese is melted. Transfer the sandwiches back to the cutting board and slice them in half before serving.
Recipe by The Colorful Kitchen at https://thecolorfulkitchen.com/2018/08/28/vegan-maple-mustard-apple-sweet-potato-melt/