Pumpkin Chocolate Croissant Bread Pudding

Name: Pumpkin Chocolate Croissant Bread Pudding
Ingredients: ½ tablespoon unsalted butter; 6 ounces pumpkin puree ((canned or fresh)); 2 large eggs; ½ cup heavy cream; ½ cup whole milk; ¼ cup sugar; Pinch of salt; ¼ teaspoon plus ⅛ teaspoon cinnamon; Pinch of nutmeg; ½ teaspoon vanilla extract; 4 croissants ((stale/day-old)); ¼ cup plus 2 tablespoons semisweet chocolate chips; ½ tablespoon turbinado sugar; Vanilla ice cream ((optional)); 4 tablespoons unsalted butter ((½ stick)); ½ cup dark brown sugar; 2 pinches of kosher salt or sea salt; 1 teaspoon vanilla extract