In a stockpot, place potato and enough cold water to corver; bring to a boil. Add 1 teaspoon salt and cook until tender, about 15 minutes. Drain.
In a food processor, blend potato, garlic, mustard, egg yolk, remaining 1/2 teaspoon salt and pepper. With machine running, gradually add oil in a slow stream until thick and blended. Add lemon juice and chives; transfer to serving bowl. (YIELD: 1-1/4 cups).
TO MAKE FRITTERS:
Preheat oven to 250ºF. Line 2 baking sheets with a double layer of paper towels.
In a medium skillet over medium heat, melt butter, and add onion and corn; cook, stirring occasionally, until onion softens, 8-10 minutes. Remove from heat; cool.
In a large bowl, combine flour, baking powder, salt, pepper and red pepper.
In a medium bowl, whisk together milk and eggs. Gradually whisk milk mixture into flour mixture just until smooth.
Stir in corn mixture and crabmeat. Cover and refrigerate 10 minutes.
Meanwhile, add enough oil to a large, heavy skillet so it reaches 1/4" deep; heat over medium-high heat.
Carefully drop 6-8 mounds of batter by level tablespoon into hot oil. Cook until golden brown, about 1 minutes per side.
Transfer fritters to paper towels; keep wamr in oven. Repeat with remaining batter.