In a large heavy-bottomed saucepan, heat the whole milk over medium heat while stirring continuously until it reaches 195°F.

In a mixing bowl, whisk together the all-purpose flour, granulated sugar, and kosher salt until well blended.

Melt the salted butter in a small saucepan over low heat, stirring occasionally until completely melted.

Combine the flour mixture with the melted butter to form a thick paste; slowly incorporate this paste into the heated milk, whisking continuously.

Bring the mixture to a gentle boil, then reduce the heat to low and simmer for about 5 minutes while stirring frequently.

Spoon the thickened Rømmegrøt into bowls and drizzle with melted butter, then sprinkle with cinnamon-sugar before serving.