Place chilli, red onion, garlic, and ginger in a food processor until finely chopped.
Heat canola oil and sesame oil in large non stick pan over medium heat
Add in the chilli mixture and cook, stirring regularly. Let cook for 7 minutes.
Add the vinegar, fish sauce and brown sugar and stir to combine it all together. Let it cook for another 3 minutes until all of the sugar has melted. Take off the heat and place in the fridge for one hour to cool.
When ready to serve, heat large wok over high heat. Add in the crab legs and then the chilli jam. Using a spatula, toss the crab in the jam until totally coated. Garnish with fresh herbs and lemon wedges. Serve immediately.