Preheat an oven to 350°F. Generously grease an 8-inch square baking pan.
Sift together the flour, cocoa powder, espresso powder, baking powder and salt into a bowl; set aside.
In a small, heavy saucepan over low heat, combine the butter and chocolate and heat, stirring occasionally, until melted, about 2 minutes. Remove from the heat and let cool slightly.
In a bowl, whisk together the eggs and brown sugar until blended. Gradually stir in the chocolate mixture until blended. Stir in the vanilla, then add the flour mixture and stir until blended.
Pour the batter into the prepared pan. Bake until the edges pull away from the sides of the pan and the center is springy to the touch, about 25 minutes. Transfer the pan to a wire rack and let cool.
Meanwhile, make the glaze: In a small saucepan over medium heat, combine the cream and espresso powder and heat, stirring, just until the powder is dissolved and bubbles start to appear around the pan edges. Add the chocolate and salt, remove from the heat and stir just until the chocolate is melted. Let cool to room temperature.
Using a small offset spatula, spread the cooled glaze over the cookie in a thin layer. Refrigerate until the glaze is set, about 30 minutes. Cut into 1 1/2-by-2 1/2-inch bars or 2-inch squares. Top each bar with a chocolate-covered espresso bean.