Lower the heat to medium and add the white wine and minced garlic to the skillet. Allow the wine to simmer and reduce by half, about 4 minutes, while using a spatula to incorporate any browned bits from the pan for added flavor.
Add the chicken broth, bouillon cube, and mustard powder. Let the mixture reach a gentle boil, then simmer for 5 minutes to allow flavors to concentrate and thicken slightly.
Reduce the heat to low. Gradually stir in the heavy cream until fully incorporated.
Stir in the lemon juice, then sprinkle in the grated Parmesan slowly, stirring constantly until the sauce is smooth. Return the chicken to the pan and allow it to warm through in the sauce.
(Optional) Stir in 2 tablespoons of cold butter for a richer, silkier finish.