Timely thread as just this past week I started perfecting a foie gras burger using home ground 50/50 chuck and sirloin. Fresh foie gras, blend of chopped exotic mushrooms and endive were common to the three samples and everyone said it was the best burger they've ever tasted. Cheese of choice was Gruyere and I'm still experimenting with the bread. Next round I'll see how short rib meat works and do more tweeks.
Years ago I tried double grinding in the past but it was mushy.
I don't get anyone who sticks only with one recipe claiming it's the best or only way to go. I have a lot of my favorite cigar, Habana Montecristo 2's, but my humidors are stocked with plenty of others.