MAKES ABOUT 24.
Preheat oven to 350°F. Butter 13 x 9 x 2-inch baking pan. Melt butter and chocolate in heavy medium saucepan over medium-low heat, stirring until smooth. Mix in 1 3/4 cups sugar and espresso powder. Remove from heat. Stir in vanilla. Mix flour, cinnamon, nutmeg and salt in large bowl. Add chocolate mixture and eggs and stir just until blended. Stir in chocolate chips.
Pour batter into prepared pan. Bake until tester inserted into center comes out with moist crumbs attached, about 30 minutes. Transfer to rack; cool completely. (Can be made 1 day ahead. Cover with foil and store at room temperature.)