Melt butter on medium heat.
Add cream cheese and cheddar and stir until fully melted.
Remove from heat.
Meanwhile, beat 2 egg whites until stiff. Fold into cheese mixture.
Cut crust off bread and cut bread into 1" cubes.
Dip cubes into cheese mixture using a skewer.
Shake off excess cheese mixture.
Place cubes on an ungreased cookie sheet.

Bake at 350 degrees 10-12 minutes until lightly browned.

To freeze: Place cubes on a cookie sheet before baking.
When cubes are frozen, layer into freezer safe container.
Thaw before cooking.