Special equipment: a deep-frying thermometer
Peel the beets and potato and grate them on the coarse holes of a box grater. Toss with the salt and place in a colander. Squeeze the mixture and press with your hands to extract as much liquid as possible.
Combine the hot water, gelatin powder, chili powder, onion powder and pepper to taste in a bowl and stir until dissolved. Pour the mixture over the grated beets and potatoes and mix quickly to distribute.
Divide the mixture into 3 equal parts and place each on its own long sheet of plastic wrap. Form into cylinders approximately 3/4- to 1-inch thick and wrap tightly in plastic wrap. Place in the freezer to firm, 8 hours or up to overnight.
Add 2 inches of oil to a high-sided saute pan and heat over medium-high heat until it registers 375 degrees F on a deep-frying thermometer.
Unwrap the rolls and slice into 1-inch pieces. Fry in batches until golden brown, 3 to 4 minutes per batch. Drain on a rack and sprinkle with salt before serving with the Spiced Yogurt and Avocado Crema.
In a food processor, pulse together the cilantro, oil, lime extract, cumin, salt, black pepper, avocado and jalapeno until blended together smoothly. Add the yogurt and blend until smooth and creamy. Taste and adjust the seasoning with lime extract and salt.