Preparation Position rack in center of oven and preheat to 350°F. Line 2 large rimmed baking sheets with parchment paper. Stir chopped chocolate in top of double boiler set over simmering water until melted and smooth; remove from over water. Cool melted chocolate 10 minutes. Meanwhile, sift flour, cocoa powder, baking powder, and salt into medium bowl. Using electric mixer, beat sugar and butter in another medium bowl until crumbly. Add eggs, 1 at a time, beating well after each addition. Continue to beat until mixture is light, pale, and creamy, about 5 minutes. Add lukewarm melted chocolate and vanilla and beat just until blended. Fold in dry ingredients, then chocolate chips. Drop chocolate cookie batter by 1/4 cupfuls onto prepared baking sheets, spacing 2 inches apart. Bake cookies, 1 baking sheet at a time, until tops are evenly cracked but cookies are not yet firm to touch, about 16 minutes. Cool cookies completely on baking sheets. Using metal spatula, carefully transfer 4 cookies to each of 4 large resealable plastic bags, arranging in single layer. Freeze cookies overnight. (Can be made 3 days ahead. Keep frozen.)
Preparation Position rack in center of oven and preheat to 350°F. Line 2 large rimmed baking sheets with parchment paper. Stir chopped chocolate in top of double boiler set over simmering water until melted and smooth; remove from over water. Cool melted chocolate 10 minutes. Meanwhile, sift flour, cocoa powder, baking powder, and salt into medium bowl. Using electric mixer, beat sugar and butter in another medium bowl until crumbly. Add eggs, 1 at a time, beating well after each addition. Continue to beat until mixture is light, pale, and creamy, about 5 minutes. Add lukewarm melted chocolate and vanilla and beat just until blended. Fold in dry ingredients, then chocolate chips. Drop chocolate cookie batter by 1/4 cupfuls onto prepared baking sheets, spacing 2 inches apart. Bake cookies, 1 baking sheet at a time, until tops are evenly cracked but cookies are not yet firm to touch, about 16 minutes. Cool cookies completely on baking sheets. Using metal spatula, carefully transfer 4 cookies to each of 4 large resealable plastic bags, arranging in single layer. Freeze cookies overnight. (Can be made 3 days ahead. Keep frozen.)