1.) Add eggs to ricotta, one at a time. Beat thoroughly with the addition of each egg.
2.) In a separate bowl, mix sugar and flour together.
3.) Introduce cheese and egg mixture to the flour bowl. Fold in milk and vanilla (and liqueur if desired).
4.) Pour into a 13-inch greased pan.
5.) Bake at 175°C for 50 to 60 minutes until firm.