How to Make It
Using a knife, cut into the side of each chicken breast half to create a pocket; do not cut all the way through. Season the pockets with salt and pepper and stuff them with the Fontina, prosciutto and basil leaves. Close the chicken pockets, tucking in any filling. Pound with a meat pounder to flatten slightly.
In a large nonstick skillet, heat 2 teaspoons of the olive oil until shimmering. Season the chicken with salt and pepper and cook over moderately high heat, turning once, until golden and cooked through and the cheese is beginning to melt, about 12 minutes. Transfer to plates, cover loosely and keep warm.
Add the remaining 1 teaspoon of olive oil to the skillet along with the shallot and cook over moderate heat until softened. Add the tomatoes and cook, tossing, until heated through, about 2 minutes. Add the vinegar and cook until nearly evaporated, about 30 seconds. Add the stock, season with salt and pepper and simmer until slightly reduced, about 2 minutes. Spoon the tomato sauce over the chicken and serve.
Notes: One serving 270 calories, 8 gm total fat, 4 gm saturated fat, 7 gm carb.