Preheat oven to 300 degrees.\nPlace the cubed bread in a single layer on a parchment-lined baking sheet and bake until lightly golden and dried, about 20 minutes. Remove from the oven and let cool slightly. Alternatively, cube your bread the day before and let it dry out overnight!\nGrease the inside of a 6-quart slow cooker with butter.\nIn a small bowl, whisk together the eggs, half-and-half, 2 Tbsp granulated sugar, brown sugar, maple syrup, vanilla, 1 Tbsp India spice, salt and raisins.\nTransfer bread to the slow cooker bowl (or other large bowl) and pour custard mixture over top. Mix gently to combine. Place a plate or other clean, weighted object on top of the bread to submerge completely. Cover and refrigerate, allowing the bread to absorb the liquid, for at least 1 hour, up to overnight.\nRemove casserole from the refrigerator and bring to room temperature. Return bowl to the slow cooker. Cover and cook on low for 2 ½ - 3 hours, until custard is set.\nRemove casserole from the heat and let cool slightly. Dust with powdered sugar and drizzle with warm maple serve. Serve warm!