Toast the bread slices in the oven at 220°C/430°F. After 8 minutes, take the bread slices from the oven and let them cool.
Pulse the bread slices in a food processor until you get medium-coarse breadcrumbs. Transfer it to the mixing bowl.
Then pulse the walnuts in a food processor until it is coarse in size. Transfer half of them to the mixing bowl. Keep pulsing the remaining walnuts in a food processor until it is fine-sized. Transfer them to the mixing bowl as well.
Add all the remaining ingredients to the mixing bowl, then mix them well until combined. Rest for about 30 minutes before serving.
Scoop the mixture using a cookie scoop, then arrange it on a serving plate.