Add butter, sugar and condensed milk to mixer and beat until mixture is pale and fluffy. Stir in the flour.
Divide mixture into as many different flavours as you wish. Gently stir flavourings into each portion.
Bake at 180c for 12-15 minutes. Roll any portions you will be freezing into a log shape and wrap in cling wrap before freezing.
To bake frozen portions, slice the logs and bake as above.