Finished! The Butter or Shortening Is Incorporated
You can see how the lumps of butter (in this case) are still visible in the flour mixture. Lumps like this would qualify as "pea-sized."By the way, at this stage you may refrigerate the dry ingredients with the fat cut in and hold it for baking later. Once you add any wet ingredients like water, eggs, milk or whatever, you've got to finish the recipe and bake it right then, as the moisture will activate the leavening agents — your baking powder or baking soda, depending on the recipe.
Interestingly, fat isn't considered a liquid in this context — not even oil. That's why deep-frying is considered a form of dry-heat cooking.
One exception to the make-ahead procedure described above is that if you're using melted butter, as when making muffins, you can't hold the ingredients. That's because the only way to melt butter is to heat it, and heat will activate the baking powder, too. That's why it's called "double-acting."
