Heat a deep skillet over medium-high heat with EVOO. Add beef and deeply brown, 6-7 minutes, breaking it up into pieces with a wooden spoon.
Add garlic, onions and mushrooms, and cook until mushrooms are dark and onions tender, 7-8 minutes.
Season with salt and pepper, then add the sherry to deglaze the pan. Scrape up the brown bits from the bottom of the pan and reduce liquid, 1 minute. Add Worcestershire and tomato sauce, and stir to combine. Reduce heat to low and cook 5 minutes more. Preheat broiler.
Spread rolls with softened butter and sprinkle heavily with parsley. Toast rolls until charred at edges. Top roll bottoms with sloppy mixture and some shaved manchego cheese. Set roll tops in place and serve. Olé!