First, prepare your keto ladyfingers according to their recipe. While they're baking or cooling, you can start on the creamy filling!
In a heatproof bowl, combine the egg yolks and your chosen keto sweetener. Whisk them well until they're light and smooth.
Place this bowl over a saucepan with gently simmering water (creating a double boiler effect). Cook over low heat for about 10 minutes, continuously whisking. In the final 2 minutes, stir in the vanilla bean paste (or extract). Remove from heat and let this delightful mixture cool completely.
In a separate, chilled bowl, whip the cold heavy cream with a hand mixer until it forms beautiful, stiff peaks. This will make your tiramisu extra fluffy!
Once the egg yolk mixture has cooled, gently fold in the mascarpone cheese until everything is smooth and well combined.
Now, carefully fold in the whipped cream into the mascarpone-egg yolk mixture in three additions, maintaining that airy texture.
Get your 8x8-inch glass dish ready. Briefly dip half of your keto ladyfingers into the cooled coffee. Make sure they absorb enough coffee to be moist but not soggy, then arrange them in a single layer at the bottom of the dish.
Spread half of your creamy mascarpone mixture evenly over the coffee-soaked ladyfingers.
Using a fine mesh sieve, dust a generous layer of unsweetened cocoa powder over the cream. Repeat steps 7-9 with the remaining ladyfingers and cream mixture.
For the best flavor and texture, chill your tiramisu in the refrigerator for at least 4-6 hours, or even better, overnight. Just before serving, give it a final dusting of cocoa powder for that perfect finishing touch!