Makes: 8 servings at 81¢ each. Prep: 1 hour. Chill: 1 hour 10 minutes. Cook: 6 minutes. Bake: at 375° for 30 minutes.
Reserve 2 tablespoons of the finely chopped walnuts.
Combine remaining walnuts, flour, 1 teaspoon sugar and salt in medium-size bowl. Add butter; beat on low speed 1-1/2 to 2 minutes or until texture of cornmeal with some large particles.
Beat together water and egg yolk in small bowl. Add to walnut-flour mixture; beat on low speed until dough begins to come together and no dry particles remain.
Turn dough out onto sheet of plastic wrap; knead lightly 8 to 10 times. Flatten into disk; wrap. Refrigerate for 1 hour.
Bring cream and sugar to boiling, stirring to dissolve sugar. Reduce heat to low; simmer until slightly thickened, about 6 minutes. Remove from heat. Stir in cinnamon, cherries and 1-1/2 cups walnuts.
Line 9-inch pie plate with plastic wrap. Spoon cherry mixture into pie plate, spreading evenly. Refrigerate until ready to prepare crostata. (Mixture seems liquid, but firms on chilling and some of liquid is absorbed.)
Heat oven to 375°F. To prepare crostata, lightly sprinkle flour on sheet of parchment paper. Lightly sprinkle flour on pastry disk and rolling pin. Roll out dough on paper into 12-inch circle (dough is very delicate but resilient). Slip dough and parchment onto large baking sheet. Invert cherry-walnut mixture onto center of dough; remove plastic wrap. Using parchment as guide, lift edges of dough and drape over filling to enclose all but center 3 to 4 inches of filling; dough will pleat attractively as it falls into place. Trim any visible parchment around edge. Refrigerate crostata 10 minutes.
Whisk egg yolk in small bowl. Brush over top of dough. Sprinkle with reserved 2 tablespoons walnuts and the sugar.
Bake in 375°F oven for 30 minutes or until golden brown and bubbly. Remove from parchment to wire rack and cool.