Oh! One more thing - this may have been covered, but a great way to add fat to your ground beef is to add softened butter to it ala Julia Child - her Biftek Haché à la Lyonnaise recipe. I made this frequently, but I skip the step where she wants us to roll the patties in flour. My family goes crazy for these.
Style Recipe - Julia Child’s Biftek Haché à la Lyonnaise (Ground Beef with Onions and Herbs)