Melt the butter in a small saucepan over medium heat. Add the minced garlic and cook for 1–2 minutes, until fragrant.
Whisk in the chicken broth and Dijon mustard, then bring the mixture to a gentle simmer.
In a small bowl, whisk together the heavy cream and cornstarch until smooth. Reduce the heat to low and slowly whisk the slurry into the saucepan.
Cook for 3–4 minutes, stirring constantly, until the sauce is smooth and thick enough to coat the back of a spoon. Season with salt and pepper to taste, then serve warm.
Notes
Cook the garlic just until fragrant to prevent bitterness.
Keep the sauce at a gentle simmer for the smoothest texture.
Whisk the cream and cornstarch together until completely smooth before adding.
Taste before serving and adjust the salt and pepper as needed.