For the onions: Melt butter in a skillet over medium heat. Add onions and soften 6-7 minutes then season with salt. Add beer and stock, bring to a bubble then reduce heat and simmer 20-30 minutes. Stir in parsley and reserve.
Combine ground meats with a liberal amount of salt and white pepper. Add spices and combine. Let stand 30 minutes. Form 6 patties thinner at the center and thicker at edges for even cooking.