Melt butter in a large Dutch oven; add bacon, and sauté until crisp. Remove bacon, and reserve for other uses.
Add peas, onions, mint, and boiling water to pan drippings. Cover and simmer 20 minutes or until peas are tender. Drain and set aside; keep warm.
Combine egg yolks, whipping cream, salt, and pepper; stir well. Pour sauce over peas and onions.