Make Ahead: The green beans can be blanched up to 1 day ahead; the mushrooms can be prepared up to 2 hours ahead. Green beans and bacon go together like, well, turkey and gravy. Portobello mushrooms, full of meaty flavor, are a fine addition to this classic dish. However, sauteed portobellos often give off a lot of dark liquid, which some cooks feel ruins the look of a dish. Scraping the dark gills out of each portobello cap with a spoon solves the problem.