Grind 2 Teaspoons Juniper Berries, The Allspice Berries, And The Peppercorns In A Spice Grinder Until Coarsely Ground, Then Stir In The Salt. Press The Ground Spices Into Both Sides Of The Flank Steak; Set Aside To Marinate At Least 30 Minutes. Bring Beef Broth And Remaining Juniper Berries To A Simmer In A Small Saucepan Over Medium Heat. Simmer Until The Broth Has Reduced By 1/4, About 5 Minutes. Stir In Heavy Cream And Gin. Return To A Simmer, And Cook Until Reduced By Half, About 10 Minutes. Keep Sauce Warm Over Very Low Heat. Preheat An Outdoor Grill For Medium-High Heat And Lightly Oil Grate. Brush The Flank Steak With Olive Oil On Both Sides. Cook On Preheated Grill Until Cooked To Desired Degree Of Doneness, About 4 Minutes Per Side For Medium. Place Steak On A Plate, And Allow To Rest For 5 Minutes. Slice The Steak Thinly And Place Onto A Serving Dish. Remove The Juniper Berries From The Gin Sauce And Discard. Serve The Sliced Steak Accompanied By The Gin Sauce.