Mix the oil, honey, spring onion, garlic and lemon juice, season with salt and pepper and rub into the turkey breasts.
Cover and leave to marinade for 30 minutes.
Meanwhile, heat the oven to 190C (160C fan) 375F, gas 5.
Carefully remove the stalks from the mushrooms and chop.
Rub the mushroom caps with 2 tbsp oil and bake in the oven for 15 minutes or until tender.
Heat the remaining oil in a small pan, cook the garlic and chopped mushroom stalks for 10 minutes, season with salt and pepper and remove from the heat.
Heat a griddle pan, brush with a little oil and cook the turkey breasts for about 5 minutes on each side or until cooked through, turning through 90 degrees to make a crisscross pattern.
Stir the feta cheese and red onion through the cooked mushroom stalks and pile onto the upturned mushroom caps.
Place under a hot grill for 2 minutes until the cheese starts to brown.
Pour the meat juices over the turkey breasts and serve with the stuffed mushrooms.
Garnish with the chives, oregano and cherry tomatoes.