Make the coconut milk for the curry sauce: break up the block of creamed coconut into fairly small pieces and place in a large bowl.
Add 1 3/4 cups boiling water and leave to stand for 30 minutes.
Strain through a clean linen napkin or two layers of cheesecloth, twisting the ends of the cloth tightly to squeeze out all the moisture.
Discard the solid material left inside the cloth and heat the coconut milk.
Slice the onion finely; chop the chili pepper, discarding the seeds.
Cook the onion in the ghee over low heat in a wide, heavy bottomed saucepan for 10 minutes while stirring.
Add the chili pepper and the ginger and continue frying gently for another 5 minutes.
Stir in the flour and cook for a few seconds.
Mix the curry powder with the vinegar and stir into the onion mixture.
Start steaming the vegetables at this point; they will take approximately 12-15 minutes.
Remove the curry mixture from the heat and pour in the scalding hot coconut milk all at once while beating continuously with a whisk to prevent lumps from forming.
Return to a low heat, beat in the stock, and keep beating until the mixture acquires a velvety consistency.
Use a hand held electric beater to beat the hot sauce until it is smooth.
Season with salt and pepper and add a little lime juice or lemon juice to taste.