PURPOSE: To prevent the oxidation of contained oil components and prepare a porous dry cake having improved keeping quality, by filling an inert gas into pores of the dry cake.

CONSTITUTION: A raw material for a cake, e.g. wheat flour, is made into the form of a dough by heat and pressure, and the resultant dough is then baked in an inert gas atmosphere. As a result, the inert gas is filled into the pores of the whole porous dry cake. The porous dry cake is then wholly immersed in a paste mixed with another raw material for the cake in an inert gas atmosphere to form an airtight edible film on the whole outer surface of the porous dry cake.