Place chickpeas and 1/2 tsp. baking soda in large bowl, and cover with 3 to 4 cups water. Soak chickpeas 24 hours. Drain.Place chickpeas, remaining 1/3 tsp. baking soda, leek, parsley, garlic, lemon juice, cumin, salt, pepper, and hot sauce (if using) in bowl of food processor. Process 30 seconds to 1 minute, or until chunky paste forms.Shape 1 Tbs. chickpea mixture into compact ball, pressing out any excess moisture, and place on plate. Repeat with remaining mixture.Heat oil to 350°F in large skillet over medium heat. Add 12 falafel balls, and cook 1 to 2 minutes, or until browned on bottoms. Roll, and cook 1 to 2 minutes more, or until golden brown all over. Transfer to paper-towel-lined plate to drain. Repeat with remaining falafel balls.