In a small bowl or cup, combine the pepper jelly, mustard, oregano, garlic, and lemon juice; set aside.
POUND chicken breasts to even thickness, season the chicken breasts on both sides with salt and pepper.
In a large skillet, melt the butter over moderately high heat.
When the foam subsides, add the chicken breasts and cook, turning once, until browned, about 4 minutes per side.
Push chicken to one side, loosen the browned bits on the bottom; add onion and chicken broth, cook until onion is tender, about 7 minutes.
Add the pepper jelly mixture to the pan and coat the chicken with the sauce.
Cook until the sauce is reduced and if you get impatient, try adding some dry Italian bread crumbs to thicken it up.
Taste test and season with salt and pepper, if needed.
Transfer the chicken to plates and spoon onion sauce on top.