Preheat oven to 180 degrees C. Line baking trays with baking paper.
In a large bow, with the mixer a low speed, beat the sugar and butter until combined. Increase speed to high and beat until light and fluffy (about 5 minutes). Reduce speed to medium and beat in the ricotta, vanilla and eggs.
Reduce speed to low. Add flour, baking powder and salt; beat until dough forms.
Drop dough by level tablespoons, about 5 cm apart; onto the prepared baking trays. Bake for about 15 minutes or until biscuits are very lightly golden (biscuits will be soft). With spatula, remove biscuits to wire rack to cool.
When biscuits are cool, prepare icing. In small bowl, stir icing sugar and milk until smooth. With small spreader, spread icing on biscuits.