1. Roast garlic in oven until soft. Squeeze garlic from skins and set aside for later use.
2. Trim all excess fat from chicken and butterfly each breast into two thin slices.
3. Pound chicken slices into flat cutlets to tenderize.
5. Heat vegetable in large skillet over medium/high heat and add chicken, careful to not overcrowd pan. Cook each side until golden brown, and internally, cooked to approximately 75% doneness (the chicken will finish cooking in the oven).
6. When chicken is golden brown, remove from pan and set on paper towel to drain. Be sure to blot any excess oil.
7. When dry, set chicken cutlets in 9" x 13" baking dish and set aside.
8. Create a chiffonade of fresh spinach and set aside for the time being.
9. To begin the roux to create our sauce, cube three tablespoons of butter and melt in large saucepan over medium heat.
10. Slowly whisk 1/2 cup flour into melted butter. Whisk continuously because the butter/flour mixture can burn easier than you think.
11. Continue to whisk. You will see the mix begin to thicken, and then start to solidify. You will also notice the mixture emit a "nutty" aroma and begin to darken in color. At this point it is important to keep that whisk moving because it can go from blond to brown to black in moments!
12. As the roux reaches a deep blond or light tan color, begin to slowly whisk in the chicken stock. Whisk more rapidly to ensure all flour clumps are completely broken up and absorbed into the stock.
13. When sauce is smooth, whisk roasted garlic into the mixture and continue to cook as the sauce comes to a rolling bubble.
14. Add tsp salt and tsp pepper to sauce.
15. Add one cup of whole milk and 3 oz lemon juice. Whisk into sauce and blend thoroughly.
16. Add the chiffonade of fresh spinach into sauce and allow to cook for a few minutes to soften.