In a stainless-steel bowl, whisk the eggs until the yolks and whites are thoroughly combined. Heat a well-seasoned medium sauté pan over medium-high heat. Add the butter and shallots to the hot pan and stir to combine. Lightly season the shallots with salt and pepper and continue cooking until the shallots are translucent.
Add the chard and stir to coat with the butter, then season lightly. Add the whisked eggs, raisins, pine nuts and pancetta and season lightly with salt and pepper.
Using a wooden spoon, stir the eggs while shaking the pan (as if making scrambled eggs). Once the eggs are almost set, stop stirring and smooth out the surface of the frittata.
Using an inverted plate, carefully flip the frittata onto a plate or cookie sheet then slide it back into the pan. Continue cooking until set—about 2 to 3 minutes. Slide the frittata out onto a cutting board and cut into wedges. Serve warm or at room temperature.