Add the baby potatoes to a large pot of salted water.
Bring to a boil and cook until fork-tender.
Drain and return to the pot.
Preheat the oven to 375°F (190°C, or gas mark 5).
In a baking dish, mix olive oil and soy sauce.
Remove the stems and gills from the portobello mushroom caps.
Place them top side down in the baking dish.
To the drained potatoes, add the soy creamer, nondairy butter, nutritional yeast, scallion, garlic powder, paprika, cumin, chili powder, salt, and pepper.
Mash the mixture with a hand masher until fairly smooth, leaving a little texture.
Fill each mushroom cap with an equal portion of the mashed potatoes.
Bake for 30 minutes or until the tops are lightly browned.
Serve warm.
Notes / Tips / Wine Advice:
Wine advice:Pair with a robust Pinot Noir or a dry Riesling.