Rinse the douchi well, and soak in fresh water overnight. Soak the glass noodles separately.
Let the clams sit in well salted water for several hours. They will spit their sand out. Lift them out, leaving the sand behind.
Drain the douchi, but save the liquid. Mince douchi together with the garlic.
Stir fry the douchi and garlic in a bit of oil until aromatic. Add clams, and stir to combine.
Add the douchi liquid, soy sauce, sugar, and extra water if needed. Taste and adjust for seasoning.
Cut the glass noodles into a manageable length and stir them in.
Cover to steam the clams for several minutes, until the shells open up.
Serve immediately, with rice.