If using fresh green peas, they may need a longer simmering time to soften.
Have ready:
Melt in a soup pot over medium-low heat:
Add:
Cook, stirring, until the onion is tender, about 7 minutes. Add 2 cups of the peas along with:
Simmer, covered, until the potatoes and peas are very soft, 25 to 30 minutes. Puree the soup with an immersion blender (or in batches in a food processor or regular blender) until very smooth. Add the remaining peas to the soup and heat through. Season to taste with:
Serve with:
Or top with: