Preheat your oven to 400 degrees.

Trim the silverskin from the leg muscle & cut/trim it into two pieces of similar size & relatively uniform shape.

Peel the sweet potatoes and cut them into large cubes.

Put the cubed sweet potatoes in a large pot & cover them with salted water. Bring the water to a simmer and cook until the cubes are knife tender (about 20 minutes, depending on the cube size).

Drain off the water and add them in a blender with the cup and a third of chicken stock, quarter teaspoon of salt and lemon juice, blending to a smooth puree.

Season the venison with salt & pepper. Oil a frying pan and get it hot over high heat. Sear the venison pieces, turning, until they develop a browned crust on all sides.

Move the pan to the oven and roast until the venison reaches your desired doneness (125 degrees for rare, 130 for medium rare).

Pull the venison out of the oven and put it on a clean plate to rest, loosely tented with foil, for 15 minutes.

Slice the venison, cutting against the grain.

Rewarm the sweet potato puree in a frying pan if you need to, then spread some of it on each plate.

Top the sweet potato puree with venison medallions, Serve.