Preheat oven to 180C/350F.

Cut crusts into 3cm/1.5" pieces.

Place bread crusts in a large bowl. Drizzle over butter, tossing the bread crusts as you go (with your other hand) to evenly distribute as best as possible.

Sprinkle over 4 tbsp of sugar and cinnamon, and toss through.

Spread out over 2 baking trays.

Bake for 5 to 8 minutes until golden brown and crunchy (check the ones in the middle of the tray). The tray on the top shelf will be ready first. The bottom tray will take a couple of minutes longer.

While hot, sprinkle over the remaining 1 tbsp of sugar (1/2 tbsp over each tray). This is mainly for appearance purpose.