Preheat oven to 425°.

Cut the scallions in half to split the light and dark ends. Slice the dark green ends thinly and reserve for garnish. Chop the light ends into 1/2 inch pieces. Chop the carrots, turnip, and mushrooms into 1/2 inch pieces. If using shiitake, remove the woody stems.

Arrange the chopped light scallion, carrots, turnips and mushrooms into two mixed equal piles on two cookie sheets. Pour a tablespoon of the oil and 1/4 teaspoon salt onto each pile, and toss the vegetables until well-coated. Spread the vegetables on the sheet pans evenly.

Roast vegetables for 10 minutes, remove pans from the oven to stir the vegetables with a spatula, then return pans to the oven for 5 more minutes.

Pour the vegetable stock into a medium saucepan. Add the minced garlic, roasted vegetables, and cubed tofu. Bring to a gentle simmer, cook for 5 minutes, then turn off the heat.

Put the miso and sugar into a small bowl, and ladle in 1/2 cup of the hot broth. Stir until the miso and sugar dissolve. Pour the broth back into the pan and stir to combine.

Serve immediately, garnished with green scallion slices. Reheat any leftover soup slowly, without letting it boil, to retain miso’s beneficial qualities.