Honey-Pecan Tart with Chocolate Glaze

Boil 4 cups pecans (reserve remaining 1/2 cup for garnish) with sugar, honey, cream, milk, and salt in a 4-quart heavy saucepan over moderately high heat, stirring occasionally, until liquid is golden, about 20 minutes (mixture will appear curdled at first, but then become thick and smooth). Remove from heat and transfer mixture to a shallow bowl, then cool completely, about 40 minutes.
Roll out larger disk of dough (keep remaining piece chilled) between 2 large sheets of parchment paper or plastic wrap (or 2 overlapping sheets for each side if necessary) into a 13-inch round (1/8 inch thick), then remove parchment from top and invert dough into tart pan set on a baking sheet, pressing onto bottom and side of pan and leaving overhang. Chill shell at least 30 minutes. Roll out remaining disk between 2 large sheets of parchment or plastic wrap into a 12-inch round (1/8 inch thick) and chill on a baking sheet at least 30 minutes.
Put oven rack in lower third of oven and preheat oven to 425°F.
If nut filling is very firm, warm slightly in a saucepan over low heat until softened but not warm. Spread filling in tart shell, smoothing top. Brush overhang of bottom crust with water. Remove parchment from remaining round of dough and arrange round over tart filling, gently rolling a rolling pin along edge to seal and trim excess.
Bake tart (in pan) on baking sheet until pastry is golden, 30 to 40 minutes. Cool in pan on a rack set on a large plate 15 minutes. Carefully remove side of pan and cool tart completely, about 2 hours.
Put chopped chocolate in a shallow bowl. Bring cream just to a boil and pour over chocolate, then whisk gently (to avoid air bubbles) until chocolate is completely melted.
Pour warm glaze over top of tart and gently spread with an offset spatula to evenly cover top, allowing chocolate to drizzle down side. Let tart stand until glaze is set, at least 30 minutes.
Rinse reserved 1/2 cup pecans in a sieve, then pat dry and carefully shave very thin slices (less than 1/32 inch) using slicer, checking thickness of first shavings on a plate before starting to shave pecans directly onto tart. If you don't have a slicer, finely chop.