Put the breasts, skin side down in a glass bowl and cover with cling film
We're going to try to get a smokey flavor into the flesh side of the breast by using a cold smoking gun (polyscience or similar) and fill the bowl with smoke and let it dissipate - 3 times so the meat absorbs the flavor.
Pre-heat the oven to 200C and get a pan with a detachable handle on the stove warming up.
Score the skin in a cross hatch pattern with a sharp knife - this will allow some of the fat to render out.
Put the breasts in the hot pan, skin side down and cook for 3-4 minutes until you can see the color creep us the visible skin (you can just see it in this photo)
Turn the breasts and cook an additional minute
Pour off the excess duck fat into a second pan - we're going to use that for the duxelles
Place the breasts skin side up in the 200C oven for 8-10 minutes.
Chop mushrooms and dice the onion while getting the second pan (with the duck fat) up to heat.
fry off the diced onion until transparent, then add the chopped mushroom and fry till it has started to break down.
Add the chicken stock and cook for a minute before transferring to a heat proof stick mixing container and liquefying the mixture with a stick blender.
Rest and serve
Remove the breast from the oven and rest it for 5 minutes before (optionally) slicing into it.
Place some duxelle on a warmed plate and place a duck breast on top skin side up.