This is my much-simplified version of a recipe that's all over the place and has way too many steps and uses way too many bowls/pans. I've done my best to revise it so that all prep and baking is done in the baking utensil itself, unless you need to do some trimming of the chicken parts.
Preheat oven to 350 degrees. Slice the butter and spread out in a 9 x 12 or 10 x 10 glass or ceramic baking dish, then put that into the oven while it heats. The butter will melt in about five minutes. Take the pan out to cool slightly while you do the rest of the prep. Press the garlic right into the pan and mix it around.
Meanwhile, trim any big globs of fat from your chicken. If you're using boneless chicken breasts, you really should remove the tough tendon, a task that gives you yet another reason not to use them. If you do,, though, and you want them to cook fairly quickly, put some plastic wrap over the top of the chicken pieces and pound them to a fairly even thickness. (I use my rolling pin as a pounder.) Sprinkle the chicken with salt and pepper.
Mix the breadcrumbs into the butter and then mix in the Parmesan. (This two-step process will help make sure that the mixture is fairly cool when you mix in the cheese, as you don't want it to melt into chunks.)* Plop the chicken pieces onto the baking sheet and coat them with the butter/crumbs/cheese mixture. Press the mixture onto the chicken to get a good layer. If you have any extra crumb mixture, just pile it onto the tops of the chicken pieces.
Bake for about 30 minutes (for boneless chicken pieces) or 45-50 minutes (for bone-in chicken). Pour any accumulated juices from the pan onto the chicken once you've placed it on a serving platter, or just serve from the baking sheet and scrape any drippings onto each serving.
*If you're using the boneless chicken parts and thus baking the dish for the shorter time, you may want to pre-toast the breadcrumbs so that you're sure they'll get brown and crispy by the time the chicken is done. Just put the breadcrumbs into the oven for 10-15 minutes, stirring them around a couple of times, before you coat the chicken with them.