Preheat oven to 425 degrees F. Line a baking sheet with parchment paper.
Combine flour with baking powder and salt in a large bowl. Add cold butter and combine with a pastry cutter, two forks, or with your hands. Mix until butter is well incorporated with flour and mixture looks like coarse sand.
Slowly add buttermilk to dough, stirring constantly. Add scallions and mix dough just until combined. Wrap dough in plastic wrap and chill in the fridge for 30 minutes.
Lightly flour clean work counter and flatten dough into 1-inch thick rectangle. Fold in half and flatten dough until it's 1-inch thick. Fold dough again and flatten until it's ½-inch thick.
Cut dough into 1 ½-inch wide strips for a total of 6 strips. Grab the two ends and twist each strip in opposite directions to create a spiral effect. Repeat with the remaining strips and place biscuits on prepared baking sheet.
Brush melted butter on top and sprinkle black sesame seeds and sugar on top. Bake biscuits for 15-20 minutes or until golden brown.
Meanwhile, make dipping sauce. Whisk together sugar with water, rice vinegar, sambal, rice wine, and cornstarch in a medium pot. Bring to a boil over high heat, reduce heat to low, and simmer for 2 minutes or until thickened, stirring constantly. Remove from heat and let cool.
Spread creme fraiche in one half of a dipping bowl and pour sweet chili sauce in the other half. Serve biscuits warm with dipping sauces.
Notes
Although the dipping sauces are optional, I highly recommend serving them with the biscuits. However, you can also enjoy the biscuits with butter and they will still be delicious!