It's very important to de-grit clams. Follow my instructions (easy!) here.
To Prepare the Dashi Stock (1 hour to overnight before cooking)
In 3 cups (720 ml) of water, drop a piece of kombu.
To Prepare the Ingredients
Cut the onions in half and then cut the halves into 5 wedges. Cut the mushrooms into ¼” (5 mm) slices.
Mince the garlic and grate the ginger (keep the juice too).
Peel the shrimp and devein the back of shrimp with a skewer (the vein runs right along the back so you can insert the skewer and pull out the vein).
To Cook the Seafood Curry
Press the “Sauté” button on your Instant Pot (I use this 6 QT Instant Pot and heat 1 Tbsp vegetable oil.
When the pot is hot, add the onion and coat with oil. Then add minced garlic and grated ginger.
Add all the seafood (clams, shrimp, calamari, and bay scallop). Add ¼ cup (60 ml) white wine to deglaze the bottom of the pot with a wooden spoon. The brown bits (called fond) stuck to the bottom of the pot are where all the flavors are.
When the alcohol is evaporated, add the kombu dashi (kombu water you made) and add the mushrooms.
Add the curry roux (or homemade curry roux) and freshly ground black pepper. Use spatula to push down the ingredients but keep the curry roux blocks on top so they won’t get stuck and burn at the bottom.
Cover and lock the lid. Make sure the steam release handle points at “sealing” and not “venting”. Press the “Keep Warm/Cancel” button on the Instant Pot to stop sauté. Press the “Pressure” button to switch to the manual pressure cooking mode. Change to "low" pressure and press the “minus” button to change the cooking time to 5 minutes.
[stove-top pressure cooker] Cook on high heat until high pressure is reached. Then reduce the heat to low but maintain low pressure for about 5 minutes.
When it is finished cooking, the Instant Pot will switch automatically to a “Keep Warm” mode. Immediately quick release the pressure/steam by sliding the steam release handle to the "Venting" position until the float valve drops down. Important: We don’t want to naturally release seafood curry because the seafood could be overcooked with the remaining heat. Unlock the lid and add 1 Tbsp soy sauce and grate ¼ of apple. Mix well and make sure all the curry roux has been dissolved.
Serve the curry over steamed rice.
You can keep the leftovers in an airtight container and store in the refrigerator for up to 3 days.