Lay the sliced spam onto a baking sheet lined with parchment paper.
Bake at 375°F/191°C for 15-20 minutes, flipping halfway through, until lightly browned.
Remove from the tray and drain on paper towel. Let cool.
Prepare the egg sheet:
Combine scrambled egg and 2 tablespoon water in a small baking pan lined with parchment paper.
Pour the egg mixture into the tray and bake at 350°F/177°C for 20 minutes, or until the egg is set.
Remove from oven and cool on a wire rack.
Cut the egg into 8 pieces, about the same size as the luncheon meat.
Make the dough:
In a bowl, add the warmed milk, granulated sugar and yeast. Give it a stir and let the yeast activate.
To a stand mixer bowl fitted with a dough hook attachment, add the flour, egg, salt, and oil. Add the activated yeast mixture and knead until the dough becomes smooth and shiny, about 5-8 minutes.
Transfer the dough to a lightly greased bowl and cover with a tea towel.
Let the dough rise in a warm location until doubled in size, about 1-1.5 hours, depending on how warm it is.
Once the dough has doubled in size, deflate it and divide into 8 portions, about 75g each (note: with the remaining extra dough, you can make regular buns).
Assemble:
Roll each portion of dough out into a oval/rectangular shape about 6" in length and about 2.5" side (or the width of the SPAM).
Place one slice of egg in the center of the dough.
Add a piece of SPAM on top of the egg.
Fold up the ends of the dough together to meet and pinch to seal the seam.
Flip it upside down and place seam-side down onto. a large (13" by 18") baking tray lined with parchment paper.
Repeat with the remaining buns.
Lightly cover and place in a warm location to rise, until slightly puffy.
Preheat oven to 375°F/191°C.
Once the buns are puffy, lightly brush the tops with egg wash.
Sprinkle sesame seeds on top of the buns (if using).
Bake at 375°F/191°C for 15-18 minutes, or until the bun reaches an internal temperature of 190°F/88°C.