Preheat the oven to 350 degrees . Toss the waffle chunks with the butter and spread on a parchment-lined baking sheet. toast, turning once, until crisp, about 7 minutes.
Meanwhile, in a large nonstick skillet, cook the bacon over medium heat, stirring occasionally, until crisp, 5 minutes. Using a slotted spoon, transfer to a paper-towel-lined plate. in a medium bowl, reserve 2 tbsp. of the bacon fat. Without wiping out the skillet, increase the heat to medium-high. When the bacon fat is shimmering, add the eggs and fry to the desired doneness.
Whisk the maple syrup and vinegar into the reserved bacon fat; season with salt and pepper. Toss with the spinach; divide between 2 plates. Top each with half of the bacon, half of the waffle croutons and 1 egg. Serve immeditely.