- 1 teaspoon olive oil
- 1 pound fresh white mushrooms, finely chopped
- 1 pinch salt
- 1 teaspoon butter
- 1/2 cup finely chopped onion
- 4 cloves garlic, minced
- 1/2 cup quick-cooking oats
- 1 ounce very finely shredded Parmigiano-Reggiano cheese
- 1/2 cup bread crumbs
- 2 tablespoons chopped flat-leaf parsley, packed
- 2 eggs
- 1 teaspoon salt
- freshly ground black pepper to taste
- 1 pinch dried oregano
- 5-6 leaves basil, or 2 tablespoons dried basil
- Heat olive oil in a skillet over medium-high heat.
- Add mushrooms to the hot oil, sprinkle with salt, and cook and stir until liquid from mushrooms has evaporated.
- Stir butter into mushrooms, reduce heat to medium, and cook and stir mushrooms until golden brown, about 5 minutes.
- Stir onion into mushrooms and cook, stirring often, until onion is translucent, 5 minutes.
- Remove skillet from heat and stir garlic into mushroom mixture until fragrant, about 1 minute. Transfer mixture to a mixing bowl.
- Mix oats into mushroom mixture until thoroughly combined.
- Gently stir 1 ounce Parmigiano-Reggiano cheese into mixture.
- Add bread crumbs, 1/4 cup parsley, and 1 egg; season with salt, black pepper, basil, and oregano.
- Mix together with a fork until crumbly.
- Stir in remaining 1 egg. Mixture should hold together when pressed.
- Cover bowl with plastic wrap and refrigerate at least 4 hours. For best flavor and texture, refrigerate overnight.
- Preheat oven to 450°F. Line a baking sheet with a silicone baking mat or parchment paper.
- Form mixture into small meatballs using a 2-tablespoon scoop.
- Roll meatballs lightly between your hands until smooth, if desired; arrange meatballs on prepared baking sheet.
- Bake until meatballs are lightly golden brown, 12 to 15 minutes.