Steamed Pigs in a Blanket

Name: Steamed Pigs in a Blanket
Ingredients: 2 cups (260 grams) all-purpose flour, plus more for dusting; 1 cup (128 grams) cake flour (see Cook’s Note); 6 tablespoons (75 grams) granulated sugar; 2 1/4 teaspoons instant yeast; 3/4 teaspoon kosher salt; 1 cup (236 grams) warm water (105 to 110 degrees F); 1/2 cup finely chopped scallions; 2 tablespoons (25 grams) neutral oil, plus more for the bowl; 10 links lap cheong (Chinese sausage); 2 tablespoons black sesame seeds; Chinese mustard, for serving