Preheat oven to 350°F. Set a kettle of water to boil.
Butter a shallow 2-quart baking dish; coat with granulated sugar, tapping out excess.
In a large bowl, whisk egg yolks with granulated sugar until lightened in color.
Melt chocolate and sprinkle over espresso powder. Stir until combined.
Whisk melted chocolate into lightened egg mixture (will be stiff). Set aside.
In a large, clean bowl, using an electric mixer on high, beat egg whites with salt until soft peaks form.
Whisk one-third of the whites into chocolate mixture.
Add remaining whites and gently fold in with a rubber spatula just until combined (do not over-mix). Transfer batter to prepared baking dish.
Set dish in a roasting pan and pour enough boiling water into pan to come about 1 inch up side of dish.
Bake until puffed and just set (center of cake should barely move when jiggled), 25-35 minutes.
Let cool 5 minutes; dust with confectioners’ sugar just before serving.
If using tall ceramic cups as I did, extra baking time is needed.
You can use instant coffee granules instead of espresso powder, if desired.
Pulse confectioners’ sugar and almond flour in a food processor until combined.
Sift mixture two times. Preheat oven to 375°F.
Whisk whites with a mixer on medium speed until foamy. Add cream of tartar and whisk until soft peaks form.
Reduce speed to low, then add superfine sugar. Increase speed to high and whisk until stiff peaks form, about eight minutes.
Sift flour mixture over whites. Fold until just combined.
Sprinkle espresso powder over and and fold until mixture is smooth and shiny.
Transfer batter to a pastry bag fitted with a half-inch plain round tip, and pipe three-quarter-inch rounds one inch apart on Gefen Parchment lined baking sheets, dragging pastry tip to the side of the rounds rather than forming peaks. Tap bottom of each sheet on work surface to release trapped air. Let stand at room temperature for 15 minutes.
Reduce oven temperature to 325°F.
Bake one sheet at a time, rotating halfway through, until macarons are crisp and firm, about 10 minutes
After each batch, increase oven temperature to 375°F, heat for five minutes, then reduce to 325°F.
Let macarons cool on sheets for two to three minutes, then transfer to a wire rack.
Fill as desired.