Cook the noodles according to packet instructions. Once cooked, rinse under cold water and drain thoroughly. Toss the sesame oil through the noodles.
Mix together all of the ingredients for the ponzu, along with 4 tbsp of water and 2 tbsp of the sesame seeds.
Add the butter, the 1 tbsp of sesame oil and the soy sauce to a large frying pan or wok and gently heat through. Once melted, add the brown crabmeat and mix thoroughly to break up all the crab. Take off the heat and toss through the noodles.
To serve, pile the noodles up high in a bowl and pour some of the ponzu around the noodles until it just pools on the bottom. Top with the coriander, spring onions and remaining tbsp of sesame seeds.