Leave bread out at room temperature, uncovered for a few days until it is hard and stale.
Preheat oven to 375 F.
In a bowl, whisk together the eggs, milk, pesto, salt and paprika until thoroughly combined. Add cheese and mix to combine.
Place bread in a square baking dish and toss with the green peas. Pour egg mixture over bread pieces. Toss well so that all the bread pieces are well coated and none remain dry. With your hands, press down on the mixture to make sure there are no air pockets and it is well compacted.