I have made this numerous times, having received the recipe from my aunt. It's quick, easy, and relatively inexpensive to make. And, best of all, it's pretty yummy. It goes with practically any side dish.
Place chicken breast(s) into a large ziploc bag and pour honey dijon marinade into bag, as well. I tend to use the whole bottle, since I usually make 2-3 pieces of chicken at a time. Use as much or as little as you feel comfortable with.
Allow chicken to marinate. Ideally, you would allow this to occur overnight, but depending upon the marinade you buy, it can be done in as little as an hour.
Crush about a half can of French's onions with your hand or other kitchen tool.
Roll marinated chicken in crushed onions until the entire top is covered.