Razor clams do have a more intense ‘clam flavor' compared to other varieties. This makes it perfect for the strong Asian-inspired flavors in this recipe. I just like leaving those more delicately flavored ones for more neutral flavor pairings like a simple lemon-butter sauce.
Get fresh clams – always. They just taste so uniquely sweet and naturally briny at their freshest. Well, this fact goes with any seafood in general.
Once you get home from the market, give them a thorough rinse in cold water then leave them submerged in the bowl for a couple of minutes. This will get any unwanted sediments out of their guts.
Also, take the time to go through the clams, discarding those with open shells, which is a sure indicator that they've gone bad.
As your clams soak, get your ingredients ready. Shallots, garlic, ginger, chili, cilantro, and fermented black beans. Chop them up fine to get the most flavor out of them given the relatively quick cooking time the clams will be needing.
Fermented black beans have a totally different flavor from cooked black beans and you could not substitute one for the other. These fermented types are easily available canned or bottled in the Asian section of most supermarkets.
Get all those chopped ingredients into your slow cooker. Add the soy sauce, oyster sauce, and sugar too at this point. No need for any additional salt or water as you'll later see that the clams will cook out in their natural stock which is really briny and flavorful on its own.
Get the razor clams in without disturbing those ingredients at the bottom of your slow cooker. Stirring your pot will get some of those aromatics on top steaming instead of simmering in stock at the bottom where they'll give off more flavor. Don't worry, we'll be finishing off the sauce in the end, and that will eventually coat and flavor each clam evenly.
As soon as you see those shells opening, the clams are ready. Depending on the size of the clams you have, this may take about 45 minutes to an hour and a half on a high heat setting in your crock pot. At this point, you may want to quickly go through them again. Any shells that have remained closed by this time should also be discarded.
Once they're done, take the clams out and pour your cooking stock in a large saucepan. Thicken it over medium heat by whisking in a light slurry of cornstarch and water. Adjust your seasoning, balancing the flavors with soy sauce and sugar. You may also adjust for heat by adding in more chopped chili.
Try to stay with cornstarch as a thickener and do not go with flour. Flour will give off a ‘floury' taste which you'll have to cook for an additional 15 minutes to get rid of. Also, flour will make your sauce pale-colored and cloudy as opposed to the shiny finish that cornstarch leaves.