Preheat oven to 350°F. Line 3 large baking sheets with foil; butter foil.
Place 1 1/4 cups chocolate chips in medium glass bowl. Microwave on medium-high until melted, stirring every 30 seconds, about 2 minutes. Cool 15 minutes.
Mix flour and baking powder in small bowl. Using electric mixer, beat sugar, eggs, corn syrup and extract in medium bowl until thick, about 3 minutes. Gradually beat in melted chocolate, then dry ingredients.
Mix in remaining chocolate chips; freeze 10 minutes.
Drop 7 heaping tablespoons batter on each prepared baking sheet, spacing 3 inches apart (cookies will spread).
Bake until cookies are cracked on top and softly set, about 15 minutes. Cool cookies on baking sheets 5 minutes. Using metal spatula, transfer cookies to racks and cool completely.
