Set the oven's temperature to 350°F (175°C). Butter or cooking spray should be used to grease a baking pan.
Each brioche slice should have butter on one side. Create triangles out of each slice.
Arrange half of the bread triangles in a single layer in the prepared baking dish, buttered side up. Sprinkle half of the raisins evenly over the bread.
Eggs, milk, cream, sugar, vanilla extract, cinnamon powder, and salt should all be thoroughly blended in a medium basin.
The bread and raisins in the baking dish should be covered with half of the egg mixture. To guarantee that the bread gets wet, gently press down.
Layer the remaining bread triangles on top, buttered side up, and sprinkle the remaining raisins over the bread.
Make sure the bread is completely submerged by evenly spreading the remaining egg mixture over it.
A larger roasting pan should be used, and it should be filled with boiling water so that it comes halfway up the edges of the baking dish. The custard will bake more evenly thanks to this water bath.
Bake for 40-45 minutes after gently shifting the roasting pan to the oven.