Wipe mushrooms clean with a damp cloth and remove the stems. Finely chop the stems and reserve.
In a large mixing bowl, combine 3 tablespoons of teriyaki sauce with the olive oil. Add the mushrooms, toss to coat, and let sit.
Preheat oven to 160°c. Line baking tray with parchment paper.
In a large pan, cook the sausage over medium heat until browned and fully cooked. Add the chopped mushroom stems, spring onions, and remaining 1 tablespoon of teriyaki sauce. Cook, stirring occasionally, for 3-4 minutes. Add the soft cheese and cook, stirring, until the cheese is fully melted. Stir in the breadcrumbs.
Stuff the mushroom caps with the sausage mixture. Place on prepared baking tray and bake for 35 minutes. Serve hot.