Bring water or broth to a simmer and stir in the oats. Cook 5 to 6 minutes, stirring occasionally, until thick and creamy.
Meanwhile, soft-boil one egg: lower it into simmering water, cook exactly 6 minutes, then transfer to an ice bath.
Sauté the spinach in the olive oil for 1 to 2 minutes, just until wilted, and set aside.
Off the heat, whisk two eggs and stir them into the hot oats, mixing constantly for 30 seconds until they turn glossy and custardy rather than clumping into curds.
Stir in the parmesan, spinach and spring onion.
Peel the soft-boiled egg, halve it, and place it on top. Finish with salt and pepper.