Preheat oven to 175 degrees C (350 degrees F). Grease cookie trays.
In a large bowl, cream together the 1 cup of 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 bicarbonate of soda, stir into the ricotta mixture. Drop by rounded spoonfuls onto the prepared cookie trays.
Bake for 8 to 10 minutes in the preheated oven. Allow cookies to cool on baking trays for 5 minutes before removing to a wire rack to cool completely.
To make the frosting 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 extract. Dip each cookie into the icing then dip in coloured sugar or sprinkles.