Preheat oven to 180 degrees C. Grease baking trays.
In a large bowl, cream together the 250g butter and sugar. Beat in the eggs, one at a time, then stir in the ricotta cheese and vanilla. Combine the flour, baking powder and bicarb soda, stir into the ricotta mixture. Drop by rounded spoonfuls onto the prepared baking tray.
Bake for 8 to 10 minutes in the preheated oven. Allow cookies to cool on baking tray for 5 minutes before removing to a wire rack to cool completely.
To make the icing, warm the milk, 1/2 teaspoon of butter and shortening in a small saucepan. Cook over medium heat, stirring occasionally until solids are melted. Remove from heat and gradually stir in the icing sugar and lemon essence. Dip each cookie into the icing then dip in sprinkles.