I’m Irish. I was raised on butter. Not margarine. Butter. Good Irish butter. Yellow, creamy, with a little salt.

Melted onto toast. A soft yellow layer on bread. A pat of butter on your potatoes. Fry your eggs in butter. Let butter melt on your chips.

I knew butter was important in baking, but I didn’t realize until today how carefully it should be treated:

The most common mistakes made by home bakers, pro­fes­sion­als say, have to do with the care and handling of one ingredient: butter. Creaming butter correctly, keeping butter doughs cold, and starting with fresh, good-tasting butter are vital details that pro­fes­sion­als take for granted, and home bakers often miss.

Butter is basically an emulsion of water in fat, with some dairy solids that help hold them together. But food scientists, chefs and dairy pro­fes­sion­als stress butter’s unique and sensitive nature the way helicopter parents dote on a gifted child.

“Butter has that razor melting point,” said Shirley O. Corriher, a food scientist and author of the recently published “BakeWise: The Hows and Whys of Successful Baking” (Scribner).

For mixing and creaming, butter should be about 65 degrees: cold to the touch but warm enough to spread. Just three degrees warmer, at 68 degrees, it begins to melt.

“Once butter is melted, it’s gone,” said Jennifer McLagan, author of the new book “Fat: An Ap­pre­ci­a­tion of a Mis­un­der­stood Ingredient, With Recipes” (Ten Speed Press).

Warm butter can be rechilled and refrozen,but once the butterfat gets warm, the emulsion breaks, never to return.

More, with cookie recipes, at the NYT Dining section.