Melt the butter in an 8-inch nonstick skillet over medium heat. Add the diced apples and cinnamon, and cook for 5 to 6 minutes, stirring occasionally, until the apples soften and turn golden at the edges.

Drizzle in 1 tsp of the honey, stir to coat, and take the skillet off the heat. Set the apples aside.

In a 2-quart saucepan, combine the oats, 300 ml of the milk, and salt. Bring to a simmer over medium heat, stirring often, for about 5 minutes until the oats have absorbed most of the liquid and thickened slightly.

In a mixing bowl, whisk the egg whites with the remaining 100 ml milk until just combined.

Reduce the heat to low. Whisk about 1/4 cup of the hot oatmeal into the egg white mixture to warm it up slowly, this keeps the whites from clumping when they go back into the hot pot.

Pour the tempered egg white mixture into the saucepan, whisking constantly. Cook for 2 to 3 minutes, stirring the whole time, until the oatmeal thickens further and no streaks of raw egg white remain. It should look glossy and hold its shape on a spoon, not runny or curdled.

Stir in the vanilla extract and the remaining 2 tsp honey.

Divide the oatmeal between two bowls. Top each with half the cinnamon apples and about 1/4 cup (50 g) Greek yogurt, and serve right away.