Add the red chili pepper flakes and sesame oil to a small pot, and place it over medium heat. Stir until the pepper flakes become a bit pasty in the heating pot. (The red chili pepper flakes burn easily, so do not preheat the pot.)
Add and stir fry beef, onion, garlic, and soy sauce until cooked.
Add anchovy stock and salt and boil for 3 minutes.
Whisk egg yolks and sugar in a large container together.
Heat heavy cream and vanilla extract slowly close to a boil but do not let it scald.
Pour cream mixture into egg yolk and sugar mixture slowly to temper eggs, whisking constantly.
Pour mixture into ramekins. Torch surface quickly to get rid of bubbles.
Pour boiling/hot water into a baking pan, less than 25% of the level of the ramekins.
Place ramekins into water bath.
Bake for 30-40 minutes.
Refrigerate for a couple of hours before serving, ideally overnight.
Top with sugar and torch to caramelize.
Serve immediately.
Notes
Optional: mix frozen/fresh berries with cream, matcha powder Add 1 more egg yolk for firmer custard Less time baking with small ramekins 16: 15 minutes