Pear and Chocolate Brioche Bread Pudding

Name: Pear and Chocolate Brioche Bread Pudding
Ingredients: Unsalted butter, room temperature, for baking dish; 3 ounces bittersweet chocolate, coarsely chopped; 7 ounces brioche, cut into eight 1/2-inch slices, halved diagonally; 1 1/2 pounds firm but ripe pears, such as Anjou or Bartlett (about 3), cored and very thinly sliced; 3 large eggs, plus 3 large egg yolks; 1 1/2 cups whole milk; 1 1/4 cups heavy cream; 1/2 cup packed light-brown sugar; 1 teaspoon ground cinnamon; 1/4 teaspoon fine salt; 1 tablespoon sanding or other coarse sugar