1. In a bowl of a mixer with a whisk attachment, combine the egg yolks, sugar, 2 tablespoon of the coffee, and the Cognac. Beat on medium-high speed until the mixture becomes a light and pale yellowish color, about 5 minutes.
2. Add the mascarpone cheese and beat for 2-3 minutes more.
3. In a separate bowl with a whisk attachment, beat the egg whites with a pinch of salt over medium speed until stiff peaks are formed, about 4-6 minutes.
4. Carefully fold in 1/3 of the beaten egg whites into the mascarpone mixture, and then add the remaining egg whites. Take care to blend gently until incorporated. Set aside.
5. Place the remaining coffee in a shallow bowl. Dip one side of a ladyfinger biscuit into the coffee so that is drenched, but not soggy.
6. Break the cookie in half and press into the bottom of your glass container. Top with 2 tablespoons of the mascarpone cream.
7. Using a fine sieve, dust with the cocoa powder and top with the other soaked half of cookie, pressing it down gently.
8. Top with 2 more tablespoon of mascarpone cream, dust with cocoa again. Repeat the whole step with another coffee soaked cookie, mascarpone, and cocoa. You will end up using 2 cookies per container. Repeat with the other 9 containers. Place the glasses on a tray and cover with plastic wrap and chill for at least 6 hours before serving.
9. Remove from refrigerator, dust with more cocoa powder, and serve.