Even though the chances are very low, your eggs may contain Salmonella. A custard is a liquid that is thickened with eggs. The liquid is usually some kind of milk or cream. Some custards contain whole eggs and some just egg yolks.Crust for custards can be par-baked, fully blind-baked and in the rare condition uncooked. Taste the milk before adding to your filling. It might be sour.ven though the chances are very low, your eggs may contain Salmonella. A custard is a liquid that is thickened with eggs. The liquid is usually some kind of milk or cream. Some custards contain whole eggs and some just egg yolks.