Put the Instant Pot in Saute mode. When hot, add oil, when oil shimmers, add onions, cook until soft, about 4 minutes.
When onions are done, add stock, or water. Add split peas, broccoli, and mustard greens.
Seal the Instant Pot and set on Manual for 15 minutes.
While the soup cooks, chop walnuts. Dry roast in a frying pan until aromatic and lightly browned.
When the Instant Pot signals it is done, use Instant Release.
If you want a smoother soup, blend with an immersion blender, or a blender or a food processor.
Add chopped walnuts to soup.
Add freshly cracked black pepper. Add salt if needed,
Place in bowl and add Peruvian Pearl Peppers to taste.