When making stock/broth from the bones of a roasted poultry, beef, veal, venison, ham, etc. I usually add onions, celery and carrots along with whatever other root vegetables I might have in the house (like parsnips) and garlic. I'm old school and was taught to peel the carrots, onions, garlic, etc. I now see chefs on cooking shows and in recipes just quarter./rough cut the aromatics and crush the garlic without peeling. How do you do it? The broth or stock will be strained anyway. Is there any reason to peel them? Is there be an advantage to leaving the peels/skins on in terms of flavor and nutrients?