Preheat oven to 350 degrees. Line a baking sheet with parchment paper or foil for easy cleanup.
In a medium bowl, combine cream cheese, sour cream, garlic, and Italian seasoning. Stir in crab meat, scallions, and mozzarella cheese, then season to taste with salt and pepper (I like 1/2 teaspoon salt and 1/4 teaspoon pepper). You will have about 2 cups filling.
Divide filling evenly among mushroom caps. Place on the baking sheet 1 inch apart. Bake 20 to 30 minutes or until filling is hot and bubbly.
Italian Seasoning: From a store-bought spice blend, or to make your own Italian Seasoning, in a small bowl, combine 2 tablespoons of dried basil, 2 tablespoons of dried oregano, 2 tablespoons of dried rosemary, 2 tablespoons of dried thyme, and 2 tablespoons of dried marjoram. This recipe only calls for 1 teaspoon, so store extra in in an airtight container.
Imitation crab meat: Also labeled as crab sticks, krab sticks, imitation crab, or seafood sticks, this is white fish mixed with binders and seasonings and pressed into stick form to resemble the flavor and texture of crab. Find it in the seafood department at most major supermarkets.
Shredded mozzarella cheese: This melts like a dream and I love its flavor in Crab Stuffed Mushrooms. Monterey Jack or Parmesan also work well.
Baby portobello mushrooms: Or white button mushrooms. Just be sure to clean whichever you choose (more tips about how to clean mushrooms below) and remove the stems.
Yield: This stuffed mushroom recipe makes about 16 pieces, enough for 8 servings, 2 pieces each. You will have more or fewer servings depending on the size of your baby portobello mushrooms.
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Make ahead: Make the filling 1 day in advance and refrigerate until you're ready to stuff the mushrooms.