Chop leftover pasta into shorter pieces for even mixing. Boil dry pasta in salted water until slightly undercooked, about 7-8 minutes. Drain and toss with half the butter or olive oil.

Preheat oven to 350°F (175°C) to ensure even cooking and browning of the frittata.

In a non-stick, oven-safe skillet, melt remaining butter or olive oil over medium-high heat. Sauté pancetta until crisp, about 3-5 minutes.

In a large mixing bowl, whisk together eggs, half of the grated Parmesan, and a pinch of salt and pepper. Fold in chopped pasta until evenly coated.

Pour the pasta and egg mixture into the skillet, smoothing the top. Cook on medium-low for about 4-5 minutes until the bottom firms up. Sprinkle remaining Parmesan on top.

Transfer skillet to preheated oven and bake for 10 minutes, until top is golden and set.

Remove skillet from oven, let cool slightly, then serve warm or at room temperature, cutting into wedges.