Score the duck skin in a criss-cross pattern without cutting into the meat.
Season duck with salt and pepper and sear skin-side down in a hot pan for one minute.
Flip breasts to sear the meat side for one minute, then flip back to skin-side and cook 5-8 minutes.
Combine honey and Chinese five-spice powder in a small bowl.
Remove duck from pan, brush with the honey mixture, and rest for 5-8 minutes.
Sauté chopped shallots and salt in 25g of butter until softened.
Add mushrooms and lemon juice, then cover and cook for one minute.
Pour in water, boil, and whisk in the remaining butter.
Season with salt, pepper, and fresh tarragon.
Wilt the spinach in a separate pan with oil.
Serve sliced duck over spinach with the mushroom sauce spooned around.