In a medium mixing bowl, sift together the chickpea flour, cornstarch, baking powder, salt and cayenne. Whisk in the beer. If the batter is stiff, add more beer. Allow the batter to rest for 30 minutes.
In a cast-iron pan, heat 3 to 4 inches of canola oil to 360 to 375 degrees. (It’s important that the oil be hot enough for the vegetables to cook quickly without absorbing much oil. Use a deep-fry thermometer, and make sure to bring the oil back up to temperature between batches.)
Working in batches, dip the vegetables in the batter to coat thoroughly, and carefully place in the hot oil. Cook for 1 to 2 minutes, until a golden brown crust forms.
For the yogurt:
In a small bowl, mix all yogurt ingredients. Serve with warm artichoke hearts.