This Chicken Cordon Bleu Sauce is perfectly creamy, ready in 15 minutes, and made by simply cooking butter with garlic, flour, and milk, and then seasoning with mustard, Parmesan cheese, and a pinch of thyme.
Add butter to a small saucepan over medium heat. Once melted, add the garlic and continue cooking for 30 seconds, or until fragrant.
1 tablespoon salted butter, 1 garlic clove
Sprinkle in the flour and whisk until combined. Slowly begin adding in ½ cup of the milk, 2-3 tablespoons at a time, whisking well after each addition. Stir in the cheese, mustard, salt, pepper, and thyme until smooth. Add additional ¼ cup milk, one tablespoon at a time, until your desired consistency is reached.
1 tablespoon all-purpose flour, ½-¾ cup whole milk, ¼ cup grated Parmesan cheese, ½ teaspoon salt, 1 ½ teaspoons Dijon mustard, ½ teaspoon finely chopped fresh thyme
Garlic. Make sure this is super finely minced as it will incorporate more easily into the sauce. (I use a garlic press for this!)
Dijon mustard. While yellow will work, the flavor will NOT be the same, so stick with Dijon for the smoothest bite.
Milk. Whole milk will give you the creamiest sauce, but 2% milk can also work.
Parmesan cheese. Freshly shredded or grated parmesan is best since it will melt into the sauce more easily.
Thyme. Dried can be subbed. Decrease the amount used by 1/3-1/2.
To Prep-Ahead: You can easily make this sauce a day or two before you need it, just keep it in an airtight container in the fridge. Then, warm it back up on the stove.
To Store: Keep leftovers in the refrigerator in an airtight container for up to 4 to 5 days. It is not recommended to freeze this sauce. To warm up the sauce, place it back in a saucepan and heat on low, whisking until it is smooth and warm. If needed, add a little more milk.