Add 2 tablespoons of butter to a frying pan on medium heat and saute the leeks until soft. 3 to 4 min. And remove to a plate to cool.

With a small knife slice a pocket lengthwise on each chicken breast and season with salt & pepper inside and outside of the breast

Stuff each breast with a 1/4 of the leeks

Heat canola oil in a saute pan over medium heat until hot and add chicken. Cook on each side until browned and cook to an internal temp of 165°F Fahrenheit

Melt 2 tablespoon of butter in the pan and add the mushrooms and garlic.

Saute mushrooms until golden brown. Add sherry vinegar & cook for 2 minutes. Sprinkle with flour

Cook the mushrooms for 3min more and whisk in chicken stock. Cook stirring occasionally until sauce thickens about 5 minutes

Remove chicken from the oven place on a plate or serving dish and top with mushroom gravy