Beat the eggs with the sugar until foamy. Mix in the mascarpone. With a mixer, fold in the cream stiffener and gelatin. Lastly, gently stir in the raspberries, setting aside a handful for garnish.
Dip the biscuits in eggnog and arrange in a mold. Spread with a layer of cream and repeat with a second layer of biscuits and cream (finishing with a layer of cream).
Finally, spread the raspberries set aside on top and sprinkle with chopped pistachios. Chill for a few hours before serving.