In a heavy-bottom saucepan, pour 1 quart of whole milk and heat it over medium heat, stirring continuously until it's steaming but not boiling.

Combine 3/4 cup of all-purpose flour, 1/4 cup of granulated sugar, and 3/4 teaspoon of kosher salt in a bowl, whisk until mixed.

Melt 1/2 cup of salted butter in a small saucepan over low heat, keeping an eye on it to prevent burning.

Gradually pour the flour mixture into the melted butter, stir rapidly to form a thick paste without lumps.

Slowly add the butter-flour paste to the heated milk, stirring constantly, and bring to a gentle boil for 2–3 minutes.

Reduce the heat to low and let simmer for about 5 minutes, stirring often until thickened to a pudding-like consistency.

Serve warm, ladling into bowls and drizzling with melted butter, sprinkled with cinnamon-sugar.