1. Add all ingredients A in a small saucepan and stir them until hot but not boiling (make sure all the butter is melted). Remove from the heat, add the sifted flour all at once and stir quickly with a wooden spoon or spatula until well blended.
2. Lower the heat to medium-low and keep stirring vigorously about 1min. The dough forms a smooth ball.
3. Transfer the dough into a bowl and add beaten egg little by little. Mix well after each time with a wooden spoon or spatula, until the batter is smooth and glossy. If the batter starts to be too loose, then stop and do not add the remaining of the eggs.
4. Fill the mixture in a large pastry bag, fitted with a star shape tip (about 1.2cm across).
5. Cut out several squares of parchment paper (about 7cm x 7cm) and pipe a ring onto each sheet. Heat enough oil in a heavy-bottomed pot, once hot, reduce the heat to medium-low and place one or two crullers at a time, paper side up. When the cruller starts to set you will be able to remove the parchment paper off, using chopsticks.
6. When the cruller turns lightly golden (1~2 min), flip it over and let it fry for another couple of minutes. Transfer on a cooling rack or paper towels to drain excess oil.
Make the glaze Pre-heat the oven to 200℃. Mix the confectioners’ sugar and milk in a small cooking pan, and heat until almost boiling. Dip the top of crullers into the sugar glaze and place on a on prepared baking sheet. Bake for about 3min in the oven. Remove from the oven and set on a wire rack to let it cool.