Grate the crusts on a coarse cheese grater. If you want fluffy soft panko, they're done. Put into plastic bags and freeze.
Additional note: I've been making panko in a food processor recently. You'll have finer crumbs than if you grate them by hand.
To make crisp crunchy panko, spread the grated soft crumbs on a plate and microwave for 1 minute at 800 W. Take out and leave to cool.
Microwave for another minute! Take out and cool. Repeat once more, let cool and they're done. Put into plastic bags and freeze.
Story Behind this Recipe
I couldn't get the panko I wanted in my neighborhood, so I made my own. You can use five-grain bread, whole wheat bread, or regular white bread.
The reason for microwaving the panko and then letting it cool is to evaporate the moisture. Fluff up with a fork when the crumbs are cooling. If you store crusts in the freezer packed into plastic bags, you can turn them into panko any time. (You can't keep them for very long through.) Grate the crusts after defrosting.