If using frozen, thaw and drain any liquid from ground beef.
Heat oil in a skillet. Add onion and garlic. Saute for 2-3 minutes until onion has softened.
Increase the heat to medium-high. Add ground beef, quickly spread into a thin single layer, and cook undisturbed for 2-3 minutes. Then flip the beef and break any big lumps. Keep cooking on medium-high heat for another 2 minutes until the beef is no longer pink.
Add dark soy sauce, oyster sauce, brown sugar, and chilli crisp. Give the mix a good stir and cook for another 2-3 minutes until the beef looks lightly caramelized.
Add hot water to the skillet. Place ramen block and gently press into the liquid. Leave for a minute to cook.
Sprinkle one seasoning packet(discard the other). Break and stir the noodles. Toss and let the ramen cook until al dente ( if there is no water in the skillet and ramen is still uncooked, add a couple of tablespoons of water at a time).
Serve while still warm with garnish of toasted sesame seeds, green onion, and a drizzle of chilli crisp.