How to Make It
Preheat the oven to 375°. In a food processor, pulse the spinach, parsley, arugula, chives, and mint until finely chopped. Scrape into a small bowl.
In a 10-inch ovenproof nonstick skillet, heat the 2 tablespoons of olive oil. Add the onion, season with salt and pepper and cook over moderately low heat, stirring occasionally, until softened, about 8 minutes. Add the eggs to the skillet and stir in all but 2 tablespoons of the chopped herbs; season with salt and pepper. Cook over moderately low heat, stirring occasionally, until the eggs start to set on the bottom and side, about 5 minutes. Transfer the frittata to the oven and bake until set, about 10 minutes. Slide onto a serving plate and garnish with the reserved chopped herbs. Drizzle with olive oil and serve warm.