Crumble the shortbread and mix it with the melted butter.
Spread the shortbread/butter mixture over the base of a baking dish, and let it cool in a refrigerator for about one hour.
Grate the peel of the lemons and extract their juice. Mix the cream cheese with the grated lemon peel and slowly add Bonny Sweetened Condensed Milk. When the mixture is homogeneous, add the lemon juice. The mixture should become brightly coloured.
Spread the mixture over the biscuit base, and allow it to cool for another 2 hours in the refrigerator.