Best part of smoking a full pork butt is the leftover char siu for fried rice, panfried noodles, saimin, etc.  I found this recipe from Titus Chan in the Honolulu Star Bulletin from October 2002 Honolulu Star-Bulletin Features (starbulletin.com) 

Mastering the dough is a true skill, and I enjoy practicing since the filling is already perfect. I've modified it by substituting sugar with monk fruit, using tallow instead of cooking oil and using a silicone mat to rest the dough on instead of wax paper.

This recipe brings back memories of my childhood of the 'Manapua Man' who sold these treats from his food truck after school. I'm fairly certain our immune systems are strong, blissfully unaware of his preparation methods!

Ingredients

            Dough: Makes 16

• 1/4 C monk fruit or sugar
  1-3/4 C warm water
  1 packet yeast
  3 C enriched cake flour
  3 C all-purpose flour
  2 T tallow or shortening
•  Filling: It's better to make the filling ahead of time to allow it to congeal so it doesn't leak out of the manapua during assembly.
  2 t tallow
  1 pound (1 cup) char siu (red sweet roasted pork), diced Chinese BBQ Char Siu Pork / Pork / BBQ Smoke / Recipes | Cooking with Aloha, Texas Style (cooking-with-aloha-texas-style.com)
  1 T soy sauce
  2 T oyster sauce
  1 T monk fruit or sugar
  1-1/2 C chicken broth
  2 t sesame oil
  Salt and pepper to taste
  2 T cornstarch dissolved in 4 tablespoons water

Directions

1. Dough: Dissolve monk fruit in warm water
2. Add yeast (water should be as hot as your finger can stand to touch 100-112 F).
3. Let stand 10 minutes as yeast foams and rises.
4. Sift flours together twice. Place in a large bowl.
5. Add tallow
6. Slowly add the yeast mixture, incorporating it into the flour gradually. Form into a ball.
7. Turn onto a silicone mat or use a stand mixer with a dough hook and knead 5 to 7 minutes, until smooth and elastic. Add more flour or water if necessary.
8. Place in a clean bowl and cover with a damp cloth. Let rise in a warm place for 4 hours, until at least doubled in bulk.

Filling

1. Heat tallow in a wok.

2.Add remaining ingredients,

• 2 t tallow
  1 pound char siu
  1 T soy sauce
  2 T oyster sauce
  1 T monk fruit or sugar
  1-1/2 C chicken broth
  2 t sesame oil
• except the cornstarch slurry, and stir-fry until hot.

3. Bring to a boil, then stir in slurry to thicken. 2 T cornstarch dissolved in 4 tablespoons water

4. To assemble manapua: Remove warm dough from bowl and knead on silicone mat 5 to 7 minutes, adding more water if too dry, or more flour if too wet.

5. Form into a long roll and divide into 16 equal portions or divide dough in half for easier handling. Lightly oil a Chinese knife or cleaver.

6. Place a section of dough cut-side down on a flat surface and pound with the flat side of the knife. Then press down on the dough with the knife and turn the knife clockwise to form the dough into a thin circle, about 4 inches diameter. Use the knife to lift the dough and place it in your hand.

7. Place a heaping tablespoon of filling into the circle, gather up the edges and pinch closed in the center. Place on a square of paper. (Dough is easier to work with when warm. Work with half the dough at a time, keeping the remainder in a warm place.).

8. Let filled buns rise in a warm place 15 minutes, covered with plastic wrap.

9. Oil steamer baskets or the pre cut steamer parchment paper and arrange buns 1/2-inch apart.

10. Fill a wok 75 percent with water and bring water to a boil.

11. Steam buns 15 minutes over high heat. If buns are in two stacked trays, switch the trays midway. Serve hot.