Rule 18 of 27 · Chapter IV — The Knife and the Cut
Cut things the same size so they cook evenly
Why this rule exists
Uneven pieces cook unevenly, and it is that simple. When your potato chunks range from thumbnail to golf ball, the small ones are mush before the big ones are tender, and you are left choosing between raw centers and burnt edges with no good option. Uniform cuts mean everything reaches doneness at the same moment, which is the whole point of cutting food up in the first place. This is not about knife-skill vanity or making things look professional, though even cuts do look better; it is about basic physics, since size determines cooking time, and mixed sizes guarantee mixed results. A cook who cuts evenly has solved half the problem of cooking evenly before the heat is even on.
In practice
Aim for consistency in size within any one ingredient, and match the size to the cooking method: small dice for quick sautés, larger chunks for long braises. When mixing ingredients that cook at different rates, cut the slow ones smaller and the fast ones larger to bring them into line, or add them to the pan at staggered times. Trim things to a flat, stable base first so they do not roll under the knife. Do not obsess over millimeter perfection; roughly even is enough, and consistent beats beautiful. Let the dish decide the shape: coins, batons, dice, or wedges each cook and eat differently.
When it doesn't apply
Rustic dishes positively want irregular, hand-torn pieces for texture and character, and there uniformity would be sterile. Some ingredients you deliberately cut in mixed sizes so a few melt into the sauce while others hold their shape. And a single ingredient roasted whole, like a halved squash, ignores the rule entirely.