With the rack in the middle position, preheat the oven to 350°F (180°C). Lightly oil a 4 x 10-inch (10 x 25 cm) loaf pan. Line the pan with parchment paper, letting it hang over two sides.
In a skillet over medium-high heat, brown the onions in the oil with the turmeric. Season with salt and pepper and let cool.
In a food processor, finely chop the potato and sweet potato. Add the cooked onions and the remaining ingredients. Purée until smooth. Season with salt and pepper. Spread the mixture in the prepared pan in an even layer.
Bake for 45 minutes or until it begins to brown. Let cool. Cover and refrigerate for at least 1 hour before serving. Unmould and cut into slices. The veggie pâté will keep in the refrigerator for up to 1 week.
Delicious served with pickled onion petal salad (see recipe) and crackers, or as a sandwich spread.
Nutritional yeast can be found in certain supermarkets and natural food stores in the form of yellow flakes or powder. It is often used in dressings, sauces and as a condiment. Nutritional yeast has been deactivated and therefore does not react like active yeast.