Fresh mushrooms can be purchased at any grocery store, though I buy a 24 oz container of them at Costco each week for my Garlic Mushrooms (recipe in The Foodie Bar Way) and on my website (www.TheNutritionProfessor.com). When choosing white button mushrooms, always look for the package with the largest mushrooms, (most health-promoting power). If I am lucky enough to find them at Farmers’ Market (see below), then I certainly pick some up. Keep them cool (right into the fridge, not left on counter), to maximize nutrient content.