Step 3: Simmer the eggs for 4 minutes for soft-boiled eggs. For semi-firm yolks and hard whites, simmer for 5 minutes. For hard-boiled eggs, simmer for 8 minutes. Use a slotted spoon to remove the egg from the water.Transfer to an egg cup and serve immediately.or semi-firm yolks and hard whites, simmer for 5 minutes. For hard-boiled eggs, simmer for 8 minutes. Use a slotted spoon to remove the egg from the water. Transfer to an egg cup and serve immediately.