Preheat oven to 230 °C.

Remove the hard, white calyx from each kidney with scissors. Open a deep pocket in each kidney without breaking through to the outer surface.

Combine the ground pork with a decent pinch each of salt, pepper, and quatre-épices. Stuff the pocket in each kidney with some of the pork mixture. Wrap each stuffed kidney with a slice of bacon and tie into place with a piece of string. Set the kidney packages in a single layer in a lightly greased roasting pan. Place a teaspoon of butter on the top of each kidney package.

Place the roasting pan in the oven and bake until the kidneys are mostly cooked, about 15 minutes.

When cooked, place the kidneys on a heated plate, set aside, and keep warm. Pour the grease out of the roasting pan and place the pan over high heat. Add the marc, flambé, and deglaze the pan. Add the cream, bring to a boil, lower heat slightly, and reduce until thickened slightly. Season with salt and pepper.

Divide the kidneys between heat serving plates and spoon the sauce over the top.