If using, finely dice the onion.

Heat the cooking oil or butter in a non-stick pan over medium heat.

Add the sliced or diced sausage (and onion, if using) to the pan and cook, stirring occasionally, until browned and heated through, about 4-5 minutes.

While the sausage cooks, crack the eggs into a bowl, add a pinch of salt and pepper, and whisk them lightly.

Pour the whisked eggs into the pan with the sausage. Let them sit for a few seconds until the edges start to set.

Using a spatula, gently push the cooked edges toward the center, tilting the pan so the uncooked egg flows underneath. Continue this motion until the eggs are mostly set but still slightly moist.

Sprinkle the grated cheese over the eggs. Cook for another 30 seconds to 1 minute, or until the cheese is melted and gooey.

Serve immediately. Garnish with fresh herbs if using.