Begin by placing a heavy-bottomed saucepan over medium heat. Pour in the whole milk and heat it until it reaches 195°F, stirring constantly with a whisk to prevent scorching.

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

In a separate saucepan, gently melt the salted butter over low heat without browning it.

Mix the dry flour mixture into the melted butter and stir to form a thick paste. Gradually add this paste into the hot milk, whisking continuously.

Lower the heat to medium-low and cook the mixture while stirring for an additional 5 minutes until thickened.

Spoon the Rømmegrøt into warm bowls and drizzle with melted butter and sprinkle with cinnamon-sugar. Serve hot.