In a heavy-bottomed saucepan, pour in the whole milk and set it over medium heat. Stir continuously as the milk heats until it reaches 195°F.

While the milk warms, whisk together the all-purpose flour, granulated sugar, and kosher salt in a mixing bowl.

In a separate small saucepan, melt the salted butter over low heat until completely liquid, then set aside.

Once the milk is at 195°F, stir the flour mixture into the melted butter to form a smooth paste, then gradually add into the heated milk, whisking continuously.

Bring the combined mixture to a gentle boil, reduce heat to a simmer, and cook for about 5 minutes, stirring often until it thickens to a pudding-like consistency.

Remove from heat and ladle warm Rømmegrøt into bowls. Drizzle with melted butter and sprinkle with cinnamon sugar before serving.