Meanwhile, heat a saucepan over medium heat and add the butter, and concentrated stock.
As the two begin to melt add the garlic and cook until everything is melted together and the garlic is fragrant, about 1 min.
Add the flour and whisk vigorously. Everything will come together in a clump. Continue to whisk for an additional 30 seconds to 1 minute to cook out the flour-y taste.
Quickly add the white wine and then the heavy cream.
Season with salt and pepper.
Whisk for a minute and reduce to a simmer, whisking occasionally, until thickened.
Add the lemon zest, and lemon juice. Continue to whisk until everything is well incorporated.
Remove from heat and serve over the chicken alongside sides such as asparagus, roasted mashed potatoes, fingerlings etc.