Drain the ricotta in a fine colander for an hour, until it's dry and firm. Meanwhile, preheat the oven to 180° C.
In a large bowl, mix ricotta, sugar, and cinnamon with a wooden spoon, then add the eggs one at a time and continue to mix to obtain a smooth and homogeneous batter. Finally, add raisins to the batter and mix them in evenly.
Grease a 20 cm hinge mold with a little butter, then sprinkle it with breadcrumbs.
Pour the batter into the mold and cook the cassola in the hot oven for about 50 minutes.
Remove the cassola from the oven and let it cool completely before removing it from the mold.
Serve cold or at room temperature.