For the Aioli: In a blender or food processor, process egg with garlic, 2 tablespoons blood orange juice, about 1/2 teaspoon zest and salt to taste. Slowly drizzle in olive oil in a thin stream until a mayonnaise forms. Adjust seasoning and add more blood orange juice or zest to taste. Pour into a serving bowl, wrap and chill until time to serve.
1. Prepare a deep fryer or pour enough oil into a saute pan so that it is 3 inches deep. Heat to 350 degrees on a deep-fry thermometer. Meanwhile, use a peeler to gently peel off any thick strings on the outside of especially thick chard stems, otherwise the stems will be fibrous. Trim the stems to 1/2- 3/4-inch thick and as long as you would like them.
2. Sift the flour into the water, whisking, until you get a very smooth batter. The water may need to be adjusted; the consistency should be similar to creme anglaise, fairly thick. Add the paprika and salt and pepper to taste.
3. Working in batches, dip the chard stems into the batter, carefully place in the oil and fry until the stems are browned and tender inside, 4-5 minutes.
4. Drain on paper towel-lined pans, and season with salt. Repeat with the remaining stems, bringing the oil back up to temperature between each batch. Serve immediately with the aglioli.