1. Start by rinsing the bulgur under cold water. Place it in a saucepan and add double the amount of water (200 ml). Bring it to a boil, then reduce to a simmer, cover, and cook for about 12-15 minutes, or until tender. Set aside when done.
2. While the bulgur is cooking, prepare the vegetables. In a separate pot, bring water to a boil. Add the chopped carrots and cook for about 5 minutes.
3. After 5 minutes, add the asparagus pieces and bell pepper to the pot. Continue to boil all the vegetables together for another 5-7 minutes, or until they are tender.
4. Once the vegetables are cooked, drain them and reserve a bit of the cooking water.
5. In a blender or food processor, combine the cooked bulgur, vegetables, and navy beans. If the mixture is too thick, add a little of the reserved cooking water or some fresh water to reach your desired consistency.
6. Blend until smooth. You may need to scrape down the sides or blend in batches to ensure a uniform purée.
7. Allow the purée to cool before serving to your baby.

Summary:
This purée is a nutritious and well-rounded lunch option for babies aged 4-10 months, providing essential vitamins, fiber, and protein from the vegetables and navy beans. It's easy to digest and can be stored in the refrigerator for up to 3 days or frozen for up to 2 months. Always ensure that you check for potential allergies with new ingredients, especially when introducing foods like beans and bell peppers.