Preheat your oven to 375°F and grab a 10-inch oven-safe skillet (cast iron works amazing here). Crack all 6 eggs into a mixing bowl, pour in the milk, and whisk until you see tiny bubbles forming on top. Add the cheddar cheese, salt, and black pepper, then whisk one more time until everything's combined and smooth.

Heat 2 tablespoons of olive oil in your skillet over medium heat until it shimmers slightly. You'll know it's ready when a tiny piece of onion sizzles immediately—don't crank the heat too high or things'll brown too fast. Toss in the diced onion and bell pepper, stirring occasionally for about 3 minutes until they soften just a little.

Add those 2 cups of fresh spinach to the skillet and stir it around for about 60 seconds until it wilts down. The spinach'll look like it takes up tons of space, then suddenly shrinks to almost nothing—this is totally normal. Once it's all wilted, spread the vegetables out evenly across the bottom of the skillet.

Sprinkle the chopped parsley and chives over the vegetables, then pour that egg mixture over everything slowly and carefully. Don't stir after you pour—let the eggs settle and flow around the vegetables naturally. The eggs'll look slightly underdone on top, and that's exactly what you want right now.

Let the skillet sit on the stovetop for about 2 minutes without touching it, just until the bottom starts to set. You'll see the edges firming up around the sides—that's your signal to transfer the whole skillet to the oven. This head start keeps everything from being rubbery later.

Bake for exactly 12 to 14 minutes at 375°F until the center's just barely set but still has the tiniest jiggle. Mine always cooks for 13 minutes perfectly, but every oven's different so start checking at 12. The top should look golden and the edges slightly pulled away from the pan.

Pull the skillet out and let it rest for 2 minutes before slicing—this makes it way easier to cut without falling apart. Slide a spatula around the edges first to loosen it, then you can either slice it into wedges right in the skillet or slide the whole thing onto a cutting board. Serve it warm, room temperature, or even cold the next day.