1. Boil the Egg: Place the egg in a small saucepan and cover it with water. Bring the water to a boil, then lower the heat and let it simmer for 10 minutes. Once cooked, remove the egg and place it in cold water to cool down.
2. Prepare the Corn: If using fresh corn, cut the kernels off the cob. If using frozen corn, ensure it is fully thawed. Steam the corn for about 5 minutes until it is tender. Allow it to cool.
3. Assemble Ingredients: Peel the egg and remove the yolk (you will only use the yolk as it is easier for babies to digest). Scoop out the avocado flesh from the half-ripe avocado.
4. Puree the Ingredients: In a food processor or blender, combine the egg yolk, avocado, and corn. Blend until smooth. If the puree is too thick, you can add a bit of water to achieve the desired consistency.
5. Serve: Spoon the puree into a baby-friendly bowl and let it cool to room temperature before serving to your baby.

Summary:
This puree is nutrient-dense, offering healthy fats from the avocado, protein from the egg yolk, and vitamins and fiber from the corn. It’s a great breakfast option for babies aged 4-10 months as it's easy to swallow and digest.

Storing Options:
Refrigerate any leftover puree in an airtight container for up to 24 hours. Before serving, ensure it is at a safe temperature by warming it up slightly and testing it.

Possible Side Effects/Allergies:
- Eggs: Be cautious if your baby has a history of food allergies. Introduce eggs separately initially to gauge any reactions.
- Corn: Some babies may have difficulty digesting corn. Monitor for any signs of digestive distress and introduce it in small amounts if uncertain.