1. To make crust, in bowl thoroughly mix flour and 1/4 tsp. salt. Cut butter in chunks and add to bowl. With two knives or pastry blender, cut butter into flour, tossing to coat with flour until largest pieces are size of pine nuts and remaining resemble coarse bread crumbs. As you work, scrape flour up from bottom of bowl, and scrape butter from knives or pastry blender. Do not let butter melt or blend completely into flour. Drizzle 1-1/2 Tbsp. cold water over flour mixture while tossing and mixing, until just moist enough to hold together when pressed. Add remaining water if needed. Turn out on plastic wrap. Gather into flank disk, pressing in any loose pieces. Wrap in plastic; refrigerate 30 minutes or up to 3 days.
2. Position rack in lower third of oven. Preheat oven to 400 degrees F. Let dough stand 30 minutes at room temperature, or until pliable enough to roll without cracking. On lightly floured surface, roll dough to 14x9-inch oval, about 1/8 inch thick, rotating and dusting with flour to prevent sticking. Brush excess flour from dough; fold in half to transfer to a piece of parchment slightly larger than dough. Unfold dough. Loosely fold and roll edge, without pressing, to form rimmed crust. Place parchment with pastry on baking sheet. Bake 10 to 12 minutes, or until light golden brown (crust edge will be a little raw inside).
3. Meanwhile for filling, melt chocolate in microwave on 50 percent power (medium) about 2 minutes. Stir frequently until chocolate is almost completely melted. Remove from microwave. Stir until melted; set aside.
4. In bowl beat egg whites with cream of tartar and vanilla until soft peaks form. Gradually add sugar and 1/8 tsp. salt. Beat until whites are stiff but not dry. Pour pecans and melted chocolate over whites; fold with spatula until batter is uniform color.
5. Remove crust from oven. Reduce oven to 350 degrees F. Dollop filling on crust. Spread to 1/2 inch thick. Bake 10 minutes, or until surface looks dry and slightly cracked (fudgy inside). Cool on baking sheet on rack. Serve warm or cool. Cover and refrigerate after 2 hours or up to 24 hours. To serve, sprinkle pine nuts and chocolate shavings. Makes 10 servings.