To make the cookies, add the soft butter and sugar to a large mixing bowl, and use a hand mixer to cream them.
Crack in the egg, and beat again until you get a smooth, creamy texture.
Add the well-drained ricotta, lemon zest and lemon extract, sift in the flour and baking powder, and use a spatula to mix everything into a sticky dough.
Refrigerate the dough for at least 1 hour, making sure the bowl is covered with a kitchen towel.
Flour 2 baking trays, and use your hands to shape walnut-sized balls out of the dough.
Transfer the dough balls onto the baking trays, making sure you leave at least one inch between each cookie.
Bake in the preheated oven at 180 degrees Celsius (350 Fahrenheit) for 15 minutes or until golden.
Remove the trays from the oven, and allow the cookies to cool down in the trays for 5 minutes, before transferring them to a cooling rack to cool down completely.
Once the are fully cooled, make the icing sugar. Sift the icing, and add enough lemon juice to make a smooth icing that is pourable, but thick enough not to run off the cookies.
Sprinkle the sprinkles around, and allow the icing to set before serving.