Bring eggs to room temperature (5–10 minutes) and preheat the oven to 400°F (200°C) if finishing under the broiler. Room-temperature eggs whisk up lighter and cook more evenly; preheating the oven lets you finish the frittata with a quick blast of heat for a golden top.

Whisk the eggs with Pecorino Romano and a pinch of salt and pepper until uniform. Whisking with cheese incorporates air and distributes the salty, savory flavor; Pecorino also adds saltiness, so keep salt light at first (you can correct later).

Heat a 9–10 inch (23–25 cm) ovenproof nonstick or well-seasoned cast-iron skillet over medium heat. Add 1 tsp olive oil and swirl to coat. Medium heat allows the fat in the pancetta to render slowly without burning—building flavor rather than bitter char.

Add the diced pancetta in a single layer and sauté 3–4 minutes, stirring occasionally, until the fat is rendered and the edges are nicely browned but not burnt. Browning the pancetta concentrates flavor and produces those savory, crisp bits that punctuate the frittata.

Add the chopped kale to the pancetta and sauté 1–2 minutes until wilted but still bright green. Tossing kale into the rendered pancetta fat briefly softens the tough leaves and picks up savory flavor—don’t overcook, you want a little texture.

Spread the pancetta and kale evenly in the skillet and pour the whisked eggs and cheese mixture over them. Allow the eggs to sit undisturbed for 1–2 minutes so the edges begin to set; this step encourages a good crust to form and helps trap the pancetta and kale in place.

Reduce heat to low and cook gently for 4–5 minutes until the edges are set but the center still has a slight jiggle. Cooking gently prevents the eggs from becoming rubbery and produces a creamy interior.

Finish the top: either transfer the skillet to the preheated oven (400°F / 200°C) for 2–3 minutes until puffed and lightly golden, or place under a broiler for 1–2 minutes watching closely. The oven/broiler gives a delicate browning without overcooking the interior—watch it so the cheese doesn’t burn.

Remove the frittata from the oven and let it rest 1–2 minutes. The carryover heat finishes the center, and resting prevents the frittata from collapsing. Taste and adjust seasoning with salt and freshly ground pepper.

Meanwhile, toast the rustic bread until golden. Cut the frittata into a wedge and serve on the toasted bread or alongside it. Garnish with the small parsley sprig and an extra sprinkle of Pecorino if desired. Serving with toasted bread gives a satisfying crunch and a vehicle to mop up the rich egg and pancetta juices.