Cube a loaf of sourdough bread into 1" pieces and leave it uncovered until it dries completely. This step takes me 24-48 hours. If you're using a fresh loaf and don't want to wait, just bake the cubed bread pieces for about 30 minutes at 300F, until they become nice and crisp. Flip them once as baking happens.If you have stale sourdough bread that isn't moldy but hard enough, skip step 1. But if using fresh sourdough bread or slightly stale loaf that is still soft, definitely start from step 1.
Preheat the oven to 320F
Pulse bread cubes. Pour them into a high-powered blender or the bowl of a food processor. Make sure not to overprocess the bread. If you want finer crumbs, pulse the sourdough bread cubes in short bursts. The rule of thumb is pulse more if you want finer crumbs and less if you prefer coarse crumbs. Depending on how much sourdough bread you have, it may be necessary to pulse the bread crumbs in batches. That's what works best for me.
I pour each done batch into a bowl and add in the seasoning and oil, tossing with a spatula so the crumbs are evenly coated.
Pour the crumbs onto a baking sheet lined with parchment paper. Spread the pieces of bread out in a single layer on the sheet.
Bake the breadcrumbs for about 15 minutes, or until they're golden brown and lightly toasted.
Cool the delicious breadcrumbs completely and refrigerate or freeze for later use.