Method

1. Trim and discard any tough stems from all mushrooms; then slice and roughly chop the mushrooms—not too finely as the mushroom pieces will shrink as they cook.
2. Heat the oil in a large sauté pan on medium heat. Add the chopped mushrooms, season with a couple pinches of salt and a little freshly ground black pepper and stir with a wooden spoon or spatula. Some liquid from the mushrooms will be released. Add the thyme and continue cooking until most of the liquid has evaporated and the mushrooms look moist and shiny—a small amount of liquid will remain. Add the shallot, garlic and celery and continue to cook, stirring until the celery is tender and translucent, 3 to 5 minutes.
3. Remove ¾ of the mushroom mixture to a mixing bowl and set aside to cool. When cool, add the breadcrumbs.
4. Leave the remaining mushrooms in the same pan for the sauce. Reduce the heat to low and add the miso paste, stirring; cook to toast the miso for about 1 minute, taking care not to burn it. Add the white wine, stirring to dissolve the miso and bring to a simmer. Continue to simmer until the wine has reduced by half. Add the tomato juice or crushed tomatoes and simmer on low heat, stirring occasionally, until the sauce is a deep red color and has thickened, about 10 minutes. Set aside.
5. Bring a medium pot of lightly salted water to a boil on medium-high heat. Set a rimmed baking sheet next to the burner. Trim any long stems from the collard greens and carefully drop each leaf into the boiling water, pressing them down with a slotted spoon to immerse them until they are bright green and the stems are tender, 30 seconds to a minute. Lift the collard leaves out of the water and place on a tray to cool. When cool enough to handle, lay each leaf on your cutting board with the back side facing up—this is the bumpy side where the stems and veins are more pronounced. Holding your knife parallel to the leaf, trim or shave the thick center stem so it is about the same thickness as the leaf (this is optional but will prevent cracking and breaking as you roll).
6. Preheat oven to 350°F.
7. Place one prepared leaf lengthwise on a flat surface with the back side facing up and the bottom of the leaf closest to you. Spoon about ¼ to 1/3 cup of mushroom mixture into a line across the base of the leaf, about an inch from the side and bottom edges of the leaf. Roll the bottom of the leaf up and over to cover the mushroom filling. Then, fold in the right side and the left side of the leaf toward the center, encasing the filling. Roll the filling toward the top of the leaf so the filling is tight and secure inside the collard leaf, like a cigar. Trim the leaf crosswise and place the roll seam side down on the baking sheet. Repeat with remaining filling and collard leaves. If a leaf is very large, you can make two rolls per leaf. When all the rolls are on the tray, drizzle with a little oil and pour about ½ cup water into the bottom of the tray before covering lightly with foil.
8. Place the tray of stuffed collard rolls in the oven to heat through until they are hot and steamy, 10 to 15 minutes. Arrange a few rolls on warm plates, spoon over the hot ragu and serve immediately.