In a large mixing bowl, combine the cooked rice, beaten eggs, sugar, salt, nutmeg, and vanilla extract. Mix until well combined.
In a separate bowl, sift together the flour and baking powder. Gradually add the dry ingredients to the rice mixture, stirring until a thick batter forms.
Heat about 2 inches of vegetable oil in a deep skillet or heavy-bottomed pot over medium heat until it reaches 350°F (175°C).
Drop spoonfuls of the batter into the hot oil, frying in batches to avoid overcrowding. Fry each fritter for 2-3 minutes on each side or until golden brown and crispy.
Remove the Calas from the oil using a slotted spoon and drain them on paper towels.
Dust the hot Calas with powdered sugar and serve immediately, either as a breakfast treat or a delightful dessert.