Preheat your oven to 300 degrees F.

Working in small-ish batches, place cubed bread into a food processor and process until the bread is as fine as you can get it. Don't worry if there are larger pieces at this point.

Spread the processed bread on a baking sheet (I really like using stoneware for this because it gets nice and toasty). Make sure it's an even layer and that there isn't overlapping.

Bake for 10 minutes. Remove from oven and stir.

From this point, the bake time will depend on how big your breadcrumbs are, how many are on the sheet, how stale it is, etc. As such, continue to bake in 10 minute increments, stirring each time you check on them. Mine usually take 20-30 minutes total.

Once the crumbs are completely toasted and dry, remove them from the oven and allow to completely cool.

Working in small batches again, run the toasted bread through a high-powered blender until they are as fine as you prefer.

Mix in optional seasonings.

Store in an air-tight container for up to 3 months or indefinitely in the freezer.