Slice your steak against the grain and very thinly. Tip: if you freeze the steak for 20-30 minutes, this will allow you to slice the steak very thinly. Transfer beef to a mixing bowl.
To the same mixing bowl, add your beef marinade ingredients. Mix with tongs or your hands and then pack the beef into a ball so that the marinade really soaks into the meat. Set aside.
In another bowl, whisk together your satay sauce ingredients until well combine. Tip: if you have a food processor or blender, add your ingredients to the blender and then blend until smooth to quicken the pace. Set aside.
Next in a non-stick pan set over medium high heat, add cooking oil and your marinated beef. Fry until the edges are brown and the meat is 50-60% cooked, about 5 minutes.
Then when the beef is 75% cooked, pour in your satay sauce and mix. Cook for 1-2 minutes until beef is cooked through, no longer red and most the liquids have evaporated.
Transfer the beef to a cutting board and finely chop your cooked beef and let it cool so it’s no longer piping hot.
Butter all slices of bread from edge to edge.
Divide the chopped beef between the two sandwiches. Pile the beef onto one piece of buttered bread and close it off with the other piece. Optional: slice off the corners and slice in half. Enjoy!