Sweet Potato Casserole with Bacon Crumble

Name: Sweet Potato Casserole with Bacon Crumble
Ingredients: 3 pounds sweet potatoes; 4 tablespoons unsalted butter; 1 sprig fresh rosemary, broken in half; 1/4 cup heavy cream; 2 tablespoons light brown sugar; 1/4 teaspoon ground cinnamon; 1 large egg, beaten; Kosher salt and freshly ground black pepper; 2 slices thick-cut bacon, cut into 1/4-inch pieces; 2/3 cup all-purpose flour; 1/4 cup chopped pecans; 3 tablespoons light brown sugar; Kosher salt; 2 tablespoons unsalted butter, at room temperature, cut into small pieces