Preheat oven to 400°.
To prepare stuffing, remove casings from chorizo. Cook chorizo, onion, and garlic in a large nonstick skillet over medium heat for 6 minutes or until browned, stirring to crumble. Drain chorizo mixture; pat dry with paper towels. Combine chorizo mixture and corn in a bowl. Combine cream cheese and sour cream in a small bowl; stir with a whisk until smooth. Add cheese mixture and salt to chorizo mixture.
Place white bread in a food processor; pulse 10 times or until fine crumbs measure 1 cup.
Fill each mushroom cap with about 3/4 teaspoon breadcrumbs. Stuff each with 2 teaspoons corn mixture; top with remaining breadcrumbs. Place on a baking sheet coated with cooking spray. Coat each mushroom with cooking spray. Bake at 400° for 20 minutes or until tops are browned.