1) Preheat the oven to 200C/Gas 6. Coat a baking sheet with cooking spray.
2) In a medium bowl, combine the chicken, broccoli (with the liquid from the package), sun-dried tomatoes (with the oil from the jar) and breadcrumbs. Toss to combine.
3) Arrange the mushroom caps, stem side up, on the prepared baking sheet. Fill each mushroom cap with the chicken mixture. Roast for 20 minutes, until the filling is golden brown and the mushrooms are tender.