Rinse the cow tongue under cold water
Trim off any excess fat or loose tissue
Place the tongue in a large pot
Add enough water to fully cover it
Add salt, onion, garlic, bay leaves, and peppercorns if desired
Bring the water to a boil
Reduce to a simmer
Cook until the tongue is tender, about 2 to 3 hours
Remove the tongue from the pot
Let it cool slightly
Peel off the outer skin while still warm
Trim away any tough base or gristle
Slice or shred the tongue as needed
Use in tacos, sandwiches, stews, or other dishes