Heat the oil in a large soup pot. Add the onion and celery and sauté over medium heat until the onion is translucent.
Add the garlic and continue to sauté until the onion is golden.
Add the potatoes, cauliflower, and enough water to barely cover the vegetables.
Stir in the seasoning blend, curry, and cumin. Bring to a gentle boil, then cover and simmer until all the vegetables are tender, about 20 to 25 minutes. Remove from the heat.
With a slotted spoon, transfer half of the solid ingredients to the container of a food processor. Process until smoothly pureed. Stir back into the soup pot with the remaining soup. Or, simply insert an immersion blender and process until half of the ingredients are pureed.
Add just enough nondairy milk to arrive at a slightly thick consistency. Return to low heat and bring to a gentle simmer.
Sprinkle the cheese in a bit at a time, stirring in each batch until melted. Stir in the peas and dill; season with salt and pepper. Simmer over low heat for a few minutes longer, stirring frequently.
If time allows, let the soup stand off the heat for several hours to develop flavor, then heat through before serving. Adjust the consistency with more rice milk if necessary; adjust the seasonings as well. Top each serving with a sprinkling of additional vegan cheddar, if desired.