In a small pot, place the Jerusalem artichokes and potatoes, cover with water, and add a pinch of salt. Cover and boil until tender.
Drain, return to pot and steam away excess water. Add 1 tablespoon butter and the cream. Puree in blender or hand held mixer, return once again to pot, add salt and pepper to taste, and keep warm.
In a small bowl, combine sugar, vinegar, mustard and black pepper. Stir in olive oil. Set aside. In another boil, combine curly and flat-leaved parsley and dates. Fold in dressing the very last minute before serving.
In a skillet over medium high heat, fry the steaks in 1 tablespoon butter, seasoning as they go in the pan. They should be cooked no more than rare, as venison differs from beef in structure and fat content.
Transfer to hot plate, cover and let rest in warm place while making the sauce. Add stock to pan and scrape out the solidified stock in the bottom with a spatula (unless it is burnt – if so you should make the sauce in a clean pan).
Add cloves and star anise, and reduce by two thirds over high heat. (As cloves and star anise differ in strength according to freshness, taste the stock as you go. Remove the spices if they start to give off to much flavor).
Stir in blackberry syrup and lemon juice and let simmer for one minute. Remove from heat and whisk in 1 tablespoon butter.