Escarole salad with mustard and guanciale breadcrumbs

First, pancetta or even bacon would work in place of guanciale, or (heresy!) just olive oil if in a pinch. And this was absolutely delicious, will make again. Recipe is from Alison Roman's Nothing Fancy.

INGREDIENTS
1 large head escarole or chicory, torn into large pieces

1 large handful parsley, tender leaves and stems

1 shallot, thinly sliced into rings
2 tbsp wine vinegar
85g guanciale or pancetta, cut into 1cm pieces
60g fresh breadcrumbs or panko
½ tsp chilli flakes
1 garlic clove, finely grated

3 tbsp whole-grain mustard
3 tbsp olive oil

DIRECTIONS

1. Combine the shallot and vinegar in a small bowl and season with salt and pepper. Leave to sit for a few minutes.
2. Meanwhile, heat the guanciale/bacon/pancetta in a large frying pan over medium-low to low heat. Cook, stirring occasionally, until the guanciale has rendered most of its fat and is starting to brown and crisp, for 10-12 minutes. Do not try to do this faster, or it will brown and crisp before the fat is rendered, and fat is what we are after.
3. Add the breadcrumbs and chilli flakes to the pan. Season with salt and pepper, and continue to cook until the breadcrumbs are nicely golden brown and toasted, for 3-4 minutes. Remove from the heat and add the garlic, stirring to mix it in.
4. Toss the escarole, parsley, mustard and shallot with the vinegar in a large bowl. Season with salt and pepper, and add the olive oil. Give the salad another toss and transfer to a large serving platter. Top with some of the toasted breadcrumbs, serving any extra alongside.