Whisk Dijon mustard and egg in a small bowl.

Combine bread crumbs, rosemary, thyme, marjoram, sage, pepper, kosher salt, and garlic powder on a large shallow plate.

Heat olive oil and butter in a large saute pan on medium-high heat.

Dip chicken breasts in the egg/mustard mixture and then dredge in the bread crumb mixture, coating evenly.

Cook chicken in the heated pan for 3-4 minutes per side, until golden brown and cooked through.

Remove chicken from the pan and keep warm.

Add chicken broth and limoncello to the pan, scraping up any browned bits from the bottom.

If desired, add lemon juice for extra lemon flavor.

Add capers, lemon slices, and parsley to the sauce and stir to combine.

Simmer for about two minutes, allowing the sauce to reduce slightly.

Place chicken breasts on plates and top with the lemon slices and sauce.