Heat a cast iron skillet or griddle pan over a medium-low heat. Pour in the olive oil and fry the chopped walnuts for 5 minutes whilst stirring regularly, then add the tamari, maple, and smoked paprika and remove from the heat after 2 minutes.
Add the garlic and spinach into the skillet and cook until wilted, then remove from the pan and set aside.
Melt the vegan butter in the skillet and arrange the potato sliced in a single layer. Sprinkle with salt and pepper and flip regularly until the sweet potato slices are tender and golden. This should roughly take 10 minutes.
Reduce the head and place the vegan cheese onto half of the sweet potato slices. Top with walnut mince and spinach, then drizzle a small amount of water into the hot skillet and immediately cover with a lid. This should help the vegan cheese melt! Once melted, top the loaded potato slices with another sweet potato slice and remove from the skillet.
Serve the sweet potato grilled cheese sandwiches sprinkled with fresh chives and enjoy them on their own, dipped into ketchup or alongside a hearty bowl of tomato soup!