PASTA

• Fine sea salt
• 1 ounce fresh spinach (about 20 leaves)
• 1 cup unbleached all-purpose flour
• 1 large egg

FILLING AND TOPPING

• 3 slices white sandwich bread
• 4 large fresh porcini mushrooms
• 1/4 cup extra-virgin olive oil
• 1 clove garlic, finely chopped
• Coarse sea salt
• Freshly ground black pepper
• 2 tablespoons finely chopped flat-leaf parsley
• 1  teaspoon finely chopped mint
• 4 tablespoons freshly grated Parmigiano-Reggiano or Grana Padano cheese

PESTO

• 1 1/4 cups packed basil leaves
• 4 tablespoons pine nuts
• 1/4 cup extra-virgin olive oil
• Fine sea salt
• 1 tablespoon cornstarch (for assembly)
   

FOR PASTA: Bring a medium saucepan of salted water to a boil. Add spinach and cook until tender, about 2 minutes. Drain in a sieve and run under cold water to cool. Squeeze water from spinach until just damp, then finely chop. 

In a large bowl, whisk together flour and pinch salt. Mound flour mixture and form a well in the center. Add spinach, egg and 2 tablespoons cold water to the well. Using a fork, gently break up yolk and slowly incorporate flour from inside rim of well. Continue until liquid is absorbed, then knead in bowl until dough forms a complete mass.

Transfer to a lightly-floured work surface and knead until smooth and elastic, about 10 minutes more. Wrap dough tightly in plastic and let rest for 30 minutes.

Bring a large pot of salted water to a boil.

Roll out dough to an 18-inch round. Cut 8 (4-inch) squares from round, discarding excess dough. Fill a large bowl with ice water. Add 4 pasta squares to boiling water and cook until squares begin to float, about 2 1/2  minutes.

Using a slotted spoon, transfer squares to ice water; submerge, then transfer to a large plate and pat dry. Repeat with remaining squares. 

FOR FILLING: Heat oven to 225º. Place bread on baking sheet and cook until dry, 18 to 20 minutes. Tear bread into pieces.

Trim mushrooms and cut stems from caps. Separately cut stems and caps into 1/4-inch-thick slices. Heat oil and garlic in a large skillet over medium-high heat until garlic is pale golden, about 2 minutes. Add mushroom slices in a single layer and cook, stirring once, until oil is absorbed, about 1 minute, then sprinkle with generous pinch salt and pepper and reduce heat to low. Cook 2 to 3 minutes (mushrooms will shed juices), then increase heat to high and cook until juices evaporate, 1 to 2 minutes more. Remove skillet from heat and stir in parsley and mint.

Pulse bread cubes in a food processor to make coarse crumbs. Add mushroom mixture and 2 tablespoons cheese; pulse just until combined.

FOR PESTO: In a food processor combine basil, 2 tablespoons pine nuts, oil and generous pinch salt. Purée until smooth. 

Heat oven to 400º.

In a small bowl, stir together cornstarch and 2 teaspoons cold water. Put 1 pasta square on a clean work-surface. Pat 3 to 4 tablespoons mushroom mixture over square to cover all but a 1/2-inch edge at the top. Using your finger, spread about 1/4 teaspoon cornstarch mixture over edge. Starting from the side closest to you, gently but tightly roll up pasta; press to seal then cut in half crosswise. Put cylinders upright and tightly together in a baking dish. Repeat with remaining ingredients, keeping cornstarch mixture stirred together as you go.

Sprinkle cylinders with remaining 2 tablespoons cheese and remaining 2 tablespoons pine nuts. Bake until warmed through, 2 to 3 minutes. Serve immediately with pesto.