Trim silver skin and icky fatty parts from your flap meat and cut them into 3 or 4-ounce chunks, or whatever size you like. Put them into a container with a tight fitting lid; don't forget to leave extra space for the marinade.

In a large bowl whisk together the Worcestershire sauce, soy sauce, molasses, brown sugar, pepper, pepper flakes, and garlic. Add the stout- careful, it will foam a bit. There is really no need to add salt; the soy and Worcestershire are plenty salty.

Pour the marinade over the tips and gently stir to coat evenly, if you don't use all the marinade it will keep for 2 weeks, refrigerated in an airtight container.

Refrigerate the meat for 8 hours or overnight. (Will keep, refrigerated for 4 or 5 days) and then cook as desired.