In an instant pot, use the saute feature and melt the butter.
Saute the onion, garlic, carrots, and celery for 3-5 minutes.
Add a pinch of salt and pepper and stir one more minute.
Turn off the saute feature and add the peas, ham shank, chicken broth, and remaining salt and pepper.
Cover with the lid and set to manual high pressure for 15 minutes.
Once it's done cooking, naturally let the steam release naturally for about 10 minutes.
While that releases pressure, chop or tear the soft pretzel up and broil for 1-2 minutes then set aside.
After the instant pot has naturally released the steam, remove the ham shank and any meat left on the bone, shred and stir back into the soup.
If your soup is too thick, at this point stir in the extra water. Taste and add more salt if necessary.
Top with croutons and enjoy!