Hamburgers Au Poivre

• 4 hamburger bun bottoms
• 900 gr beef (ground)
• 80 ml whipping cream
• 80 ml wine (red)
• 30 ml dijon mustard
• 18 gr coarsely black pepper (ground)
• 8 gr green peppercorns
• 5 gr tarragon (chopped fresh)
• 2 gr tarragon (dried)