Place kaffir lime leaf, curry leaves, and mustard, cumin, and coriander seeds in a cast iron skillet in 1 tbsp olive oil. Turn on skillet to medium heat.
When mustard seeds start to pop, remove leaves and add onion, ginger, and turmeric. Cook until onions are soft, 3-4 minutes.
In a food processor, blend sweet potato and cilantro stalks into a smooth mixture.Add black beans, and pulse until about 1/5 of the black beans are left whole.
Add black bean mixture and cooked onions to a mixing bowl. Add 2 tbsp curry paste, and mix to combine. Add and incorporate rice flour.
Form patties of your desired size. Heat oven to 400 ºF.Heat a skillet to medium heat, and add olive or avocado oil. Sear patties on both sides until golden brown.
Place skillet in oven for 4-8 minutes, depending on thickness of patties. This results in a non-mushy veggie burger.