Combine water, salt, and pepper; bring to a boil. Add peas and simmer 5 minutes.
Melt butter in a heavy sauce pan over low heat. Add the flour and cook 1 minute, stirring constantly. Gradually add milk; cook over medium heat stirring constantly until thick and bubbly. Stir the sauce into the peas.
Top with biscuits and sprinkle lightly with onion salt. Cover and cook 15 minutes or until the biscuits are done.