• Position rack in center of oven and preheat to 350°F.
• Line 2 rimmed baking sheets with parchment paper.

Melt chocolate - microwave method

• Put chocolate in a microwave-safe bowl. Microwave at high power for 55 seconds.
• Stir with a rubber spatula, scraping down the sides of the bowl, then heat 30 seconds more.
• Continue heating and stirring for 15-second intervals until the chocolate is uniformly smooth and glossy.

Melt chocolate - double boiler method

• Stir chopped chocolate in top of double boiler set over simmering water until melted and smooth; remove from over water.

Make the dough

• Cool melted chocolate 10 minutes.
• 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.

Bake

• Drop chocolate cookie batter by 1/4 cupfuls (#16 scoop) 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.
• For Ice Cream Sandwiches
• Using a metal spatula, carefully transfer 4 cookies each to each of 4 large resealable plastic bags, arranging in single layer.
• Freeze cookies overnight. (Can be made 3 days ahead. Keep frozen.)