Butterfly chicken breasts and cut in half. Salt and pepper. Heat 1 tablespoon olive oil and one tablespoon butter in large frying pan. Place chicken in pan and brown for 3 minutes on each side. It will not be cooked quite all the way. Remove chicken from pan and slice up after cooled a bit.
Add chives, mustard and lemon juice to skillet. Stir and cook for about 30 seconds.
Add chicken, stock and garlic. Stir until smooth. Bring to a boil and cook until reduced by half (about 10 minutes).
While sauce is reducing, cook pasta as directed on package. Drain but save about a half cup of the pasta water.
Add remaining butter to sauce. Add chicken and pasta to pan and stir. If needed, add some pasta water to thin slightly. If desired, add some fresh chives for garnish....freshly saved Pamesan is great with this. Serve family style.
FYI: Keep in mind that you may need to tweak the lemon and/or mustard to your own taste. My family really likes both. If it is too strong, just keep adding a half cup of broth until it gets to where you like, just don't make it bland. When you add a pound of pasta to it, that tames the flavor down considerably. Goes fabulously with a nice bottle of Chardonnay!!