Hard-boil eggs: Put eggs into a small saucepan, add enough water to cover and bring to a rolling boil over medium-high heat. Turn off heat, cover and let stand for 20 minutes. Drain, then cover eggs with ice water. Let stand until eggs are cold, about 5 minutes. Drain, then peel.
Meanwhile, bring a medium saucepan half full of water to a boil. Add peas, reduce heat and simmer until peas are tender, 7 to 10 minutes. Drain and rinse with cold water.
Cook bacon in a skillet over medium heat, stirring, until crisp, about 5 minutes. Transfer with a slotted spoon to paper towels. Pour off all but 1 Tbsp. fat from pan; add onion and garlic to pan and cook, stirring, until softened, about 5 minutes. Remove from heat. Stir in peas and bacon, followed by olive oil, vinegar and mustard. Chop eggs, add to salad and toss gently.