Rinse the ox tongue under cold water
Trim off any excess fat or debris
Place the tongue in a large pot
Cover with cold water
Add salt, onion, garlic, bay leaves, and peppercorns if desired
Bring to a boil
Reduce to a simmer
Skim off any foam that rises to the surface
Simmer until tender, about 2 to 4 hours depending on size
Remove the tongue from the pot
Let it cool slightly
Peel off the outer skin while still warm
Trim away any rough or discolored parts
Slice or use as desired in recipes