1. Begin by cooking the diced parsnip and fennel in a pot of boiling water. Boil for about 10-12 minutes until they are soft but still hold their shape. Drain and let cool slightly.
2. In a large bowl, combine the cooked rice, crumbled tofu, boiled parsnip and fennel. Mix well to combine all the ingredients evenly.
3. Add the soy milk gradually to the mixture, stirring until everything is well incorporated. The mixture should be moist but not too wet. If it’s too dry, feel free to add a little more soy milk.
4. If using, you can sprinkle in a pinch of dried thyme for extra flavor.
5. Preheat a non-stick frying pan over medium heat and add the olive oil if using.
6. Scoop portions of the mixture and form them into small patties or cakes using your hands. You can make them about the size of a child's palm for easy handling.
7. Cook the patties in the frying pan for about 4-5 minutes on each side, or until they are golden brown and firm. Be sure to flip them carefully to keep their shape.
8. Transfer the cooked rice cakes onto a plate lined with a paper towel to absorb any excess oil.
9. Allow the rice cakes to cool slightly before serving them to your toddler.

Summary:
This recipe is great for toddlers because it combines a variety of textures and flavors, encouraging self-feeding and exploration. The parsnip and fennel provide essential vitamins and minerals, while the tofu adds protein, and the rice offers carbohydrates for energy.

Storing Options:
These rice cakes can be stored in an airtight container in the refrigerator for up to 3 days, or you can freeze them for up to a month.

Possible Side Effects/Allergies:
Always be mindful of potential allergies related to soy and ensure that your baby has been introduced to all these ingredients individually before serving.