Lightly spray a 9x13-inch baking dish with a little cooking spray. Cut the bagels into small, 1-inch chunks, then toss them into the baking dish.

In a large bowl, combine the eggs, milk, cream, syrup, brown sugar, vanilla, cinnamon and salt. Whisk it up really well with a fork, then pour the egg custard mixture over the bagels and press them down into the custard so everything gets a good soaking. Sprinkle chopped pecans over the top, if using. Cover and refrigerate at least 2 hours or overnight.

Preheat your oven to 350 degrees when ready to bake the casserole. Prepare the crumble topping by combining the flour, brown sugar, cinnamon and salt in a bowl, then pouring the melted butter of the top and stirring everything with a fork to combine. Sprinkle in small clumps over the top of the casserole before sliding it into the oven.

Bake for 50-60 minutes, until golden brown on top. You might want to cover the casserole with foil during the last 20 minutes if it is getting too brown. It is done when the egg mixture that has soaked into the bagels is set without being soggy and everything is cooked through, but be careful not to overbake and dry it out.

Prepare the maple glaze, if using, by whisking together the maple syrup and powdered sugar in a small bowl.

Remove the casserole from the oven and let it cool for a few minutes. Sprinkle the berries over the top and drizzle with the maple glaze, if desired. Dust with powdered sugar and cut into large squares just before serving.