In a large heavy-bottomed saucepan, gently heat 1 quart of whole milk over medium heat until it reaches 195°F, stirring almost continuously to avoid scorching.

While the milk is heating, whisk together ¾ cup of all-purpose flour, ¼ cup of granulated sugar, and ⅓ teaspoon of kosher salt in a small bowl. Set aside.

In a small saucepan, slowly melt ½ cup of salted butter over low heat, ensuring it doesn't brown.

Once the milk reaches 195°F, stir the flour mixture into the melted butter to form a paste. Gradually whisk this into the hot milk, stirring constantly to prevent lumps.

Reduce the heat and simmer the mixture for 5 minutes while stirring often, until it thickens to a pudding-like consistency.

Spoon the warm rømmegrøt into bowls, drizzle with melted butter, and sprinkle with cinnamon-sugar before serving.