In a small pan, combine walnut halves, sugar, chili flakes, paprika, a pinch of salt, and butter. Melt the sugar and butter together for a couple of minutes, stirring to coat the walnuts. Ensure the sugar doesn’t burn.
Transfer the walnuts immediately to a sheet of parchment paper, separating them so they don’t stick together. Set aside.
In a hot skillet, cook the bacon or pancetta until crispy on both sides. Drain on paper towels.
For the dressing, combine olive oil and vinegar in a large mixing bowl with a pinch of salt and pepper. Whisk until homogenized. Add half of the gorgonzola and mash with a fork (a few lumps will remain).
Toss the spinach in the dressing until evenly coated. Divide among serving bowls.