Step 1

Stir together peas, onions, carrot, celery, garlic, bay leaves, parsley, and salt in a medium saucepan. Add stock to cover by a depth of 1 inch. Bring to a boil over high, skimming foam that rises to the top. Reduce heat to medium. Partially cover; simmer until tender, 15 to 25 minutes. Remove pan from heat; let stand 15 minutes.

Step 2

Remove and discard onions, carrot, celery, garlic, bay leaves, and parsley. Do not drain peas. (To make ahead, transfer cooked peas and liquid to an airtight container; cover and refrigerate up to 3 days.) Stir in butter, thyme, and pepper. Serve warm.