Finely chop garlic, shallot, and onion and place in a small bowl.
Add chopped fresh parsley and tarragon, Worcestershire sauce, Dijon mustard, Guinness beer, soy sauce, and seasonings then mix well to combine.
Let stand at room temperature for 30 minutes so flavors can blend together.
Marinate beef, lamb, and pork for 4 to 24 hours. Chicken and poultry for 2 to 8 hours, and vegetables and meat substitutes for 1 hour.
Once you have finished marinating, place the unused marinade in a small saucepan and reduce it for one or two minutes until slightly thickened.
Add more beer to the marinade at this stage if desired.
This can be served as a sauce or cooled completely and stored in an airtight container in the refrigerator for future use. The mixture will stay good for up 5 days.