Pound chicken breasts lightly to about ½-inch thickness.
Heat a large skillet over medium heat. Add 3 tablespoons of butter; allow to melt.
Add chicken breasts in a single layer. Sprinkle with lemon juice, salt and pepper. Brown on each side for 3 minutes. Transfer to a plate and cover.
Add remaining 2 tablespoons of butter to pan; allow to melt. Add mushrooms and minced shallot, plus a pinch or two of salt. Cook, stirring occasionally, for 5 minutes.
Stir in beef broth and cognac, scraping up any brown bits from the bottom of the pan. Bring to a steady simmer. Simmer, stirring occasionally for 2-3 minutes.
Stir in cream, bring back to a steady simmer. Bring to a low simmer. Simmer, stirring occasionally, until thickened slightly, about 2 minutes.
Reduce heat to low. Season to taste. Return chicken breasts to pan, turning to coat in sauce. Cook on low until chicken is done through.
Serve warm garnished with fresh parsley.
