Combine all the dressing ingredients in a large bowl. Mix the dressing well with a fork.
Heat a large skillet over medium-high heat, pour the dressing into it, heat well.
Put onion and garlic in a frying pan, simmer in the sauce for about 2 minutes. Then add spinach leaves in small portions, cook until the leaves wither.
Cook the potatoes in the microwave until soft, about 13 minutes. Cut each tuber in half, but not completely, loosen it slightly with a fork, and put the spinach mixture between the halves. Put 1.5 tablespoons of cheese in each serving of potatoes with spinach.