An expandable half-product or pellet suitable for cooking by microwave oven (or other method such as frying) results in a non-uniform, random design while having a distinct pattern or style. The stress cracks created by a controlled drying process help to achieve the design. Extruded half-products are first case-hardened to create an outer skin that requires an internal buildup of pressure to penetrate. After the creation of the outer skin by drying in an oven or ambient air, the half-product is heated to permit the vapor pressure of the moisture inside to break through the outer skin and escape. Such escape points induce stress cracks in random places in the half-product.
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