In a small bowl, soak the onion slices in the sherry vinegar.
In a heavy skillet over medium heat, cook the bacon until crisp, about 7 minutes. With tongs or a slotted spoon, transfer the bacon to a plate that’s lined with paper towels. Crumble when cool.
Pour off all but 3 Tbs. fat from the pan. Strain the vinegar from the onions into the pan and stir with a wooden spoon to loosen the browned bits and emulsify the dressing. Put the spinach in a medium bowl and drizzle the warm dressing over it. Toss and season with salt to taste.
Divide the spinach among four plates and garnish with the mint, walnuts, onion, and goat cheese. Sprinkle with the crumbled bacon, season with pepper, and serve.
nutrition information (per serving):
Photo: Scott Phillips