The best is making them out of fresh bread yourself. Croutons are not stale, air-dried bread. Air-drying bread results in chemical transformations beside loss of moisture that leave bread nasty tasting. You want to drive moisture from the bread quickly. This is what toasting is all about.
The goal is a crispy crumb that is light and explodes when bitten. Croutons should not be tough to chew. That defeats their purpose of lightening a salad, giving each bite a lift.
Warning: croutons must be completely dry or they will not keep and fail to achive their purpose.
|—||bread, any sort, but especially with a crumb*|
|—||aromates like garlic (optional)|
* Formally speaking, a bread's crumb is the soft or inside part in opposition to its crust.
1. Cube bread into desired size.
2. Toss cubes in oil, but do not soak them.
3. Layer on a half baking sheet not much more than one deep.
4. Bake at 350° for 12 minutes. Depending on layering and also on oven evenness (or lack thereof), you may wish to use a spatula to turn, stir or otherwise toss the cubes halfway through.
5. Cool, then seal in air-tight container. If storing more than a few days, refrigerate against the oil becoming rancid.