• Make-Ahead
• Web Exclusive
• Vegetarian

Ingredients

1. 1 stick (4 ounces) unsalted butter, plus 4 tablespoons melted butter
2. 3 medium shallots, minced
3. 1 pound shiitake mushrooms, stems discarded and caps sliced 1/4 inch thick
4. 1 pound white mushrooms, sliced 1/4 inch thick
5. Salt and freshly ground pepper
6. 1/2 cup dry sherry
7. 1 tablespoon sherry vinegar
8. 9 sheets phyllo dough
9. Sour cream, for serving

Directions

1. Preheat the oven to 375°. In a very large skillet, melt the stick of butter. Add the shallots and cook over moderate heat until softened, about 4 minutes. Add the shiitake and white mushrooms, season with salt and pepper and cook over moderately high heat, stirring occasionally, until the liquid evaporates and the mushrooms are lightly browned, about 8 minutes. Add the sherry and sherry vinegar and cook for 1 minute. Season with salt and pepper.
2. Transfer the mushrooms to a food processor and process until finely chopped but still a bit chunky.
3. Lay 1 sheet of phyllo on a work surface and brush with melted butter, then top and repeat with 2 more phyllo sheets; keep the rest covered with plastic wrap. Halve the layered phyllo to form two 8 1/2-by-12-inch rectangles. Spoon 1/2 cup of the mushrooms at the bottom of each half, leaving a 1-inch border. Roll the phyllo over the mushrooms; fold in the sides and continue to roll up like a cigar. Brush each strudel with melted butter and transfer to a large baking sheet. Repeat with the remaining phyllo, mushrooms and butter.
4. Bake the strudels for 15 minutes, or until nicely browned and crisp. Let rest on the baking sheet for 3 minutes. With a serrated knife, cut the strudels on the bias into 2-inch lengths. Transfer to a platter, cut sides up, and top with small dollops of sour cream. Serve hot.

Notes

The mushroom filling can be refrigerated for up to 2 days. Bring to room temperature before filling the phyllo.

Clean mushrooms right before using them. Wipe them gently with a damp cloth or paper towel, or rinse them quickly under cold water and dry them immediately. Do not soak them in water, because they absorb liquid like sponges. For hard-to-reach or stubborn dirt, clean the mushrooms with a soft brush (a small paint brush works well).