Place rice in fine-mesh strainer and rinse under running water, agitating rice with your hand every so often, until water running through rice is almost clear, about 1½ minutes. Bring rice and 1% cups water to boil in medium saucepan over high heat, stirring occasionally with rubber spatula to dislodge any rice that sticks to bottom of saucepan. Cover, reduce heat to low, and simmer for 30 minutes.

Transfer rice to large bowl and mash with potato masher until most grains have been crushed, about 1 minute. Let cool for 5 minutes. Whisk in remaining ½ cup water, eggs, sugar, yeast, salt, vanilla, and nutmeg until well combined and no lumps of rice larger than ¼ inch remain. Gently fold in flour until just combined. Cover with plastic wrap and refrigerate for at least 6 hours or up to 24 hours.

Adjust oven rack to middle position and heat oven to 200 degrees. Set wire rack in rimmed baking sheet and line half of rack with triple layer of paper towels. Add oil to large Dutch oven until it measures about 1½ inches deep and heat over medium-high heat to 3 75 degrees.

Stir batter well. Transfer heaping tablespoon of batter to oil, using second spoon to ease batter out of spoon; repeat portioning until there are 10 calas in oil. Fry until calas are deep golden brown, about 4 minutes, flipping

once halfway through frying. Adjust burner, if necessary, to maintain oil temperature between 350 and 3 75 degrees.

Using spider skimmer or slotted spoon, transfer calas to prepared wire rack; roll briefly so paper towels absorb grease. Transfer sheet to oven to keep warm. Return oil to 3 75 degrees and repeat with remaining batter in 2 batches. Dust calas with confectioners' sugar and serve immediately.