Butter, then line bottoms of three 8- or 9-inch round cake pans with parchment paper.
Preheat oven to 350°F.
Over low heat in a small saucepan, gently melt chocolate with coffee or hot water, stirring until smooth. Set aside to cool.
Combine lemon juice with milk in a glass and set aside to curdle.
Separate eggs and beat whites until stiff peaks form but the whites aren’t dry. Set aside.
Cream butter and sugar with electric mixer for 3-4 minutes, until light and fluffy. Add egg yolks, one at a time, beating after each addition. Stir in cooled, melted chocolate/coffee mixture and vanilla extract.
In a separate bowl, whisk together gfJules Flour, cocoa, baking powder, baking soda, and salt.
Add flour mixture to creamed sugar mixture, alternating with lemon/milk mixture and beating after each addition until smooth. Gently fold in egg whites and be sure not to over-work the batter. (See photos above recipe card)
Distribute batter evenly between the three pans. Bake in preheated oven for 24 minutes or until a toothpick inserted into the centers comes out clean.
Remove to cool on a wire rack before removing to fully cool after the first ten minutes in the pans.