Preheat the oven to 170°C.
In a bowl, put the egg whites and beat until they become a firm meringue. Add the flour, baking powder, salt, and stir.
In another bowl, put the oil, sugar and beat until fluffy. Add the egg yolks one by one and continue beating until fluffy. Add the vanilla and cognac. Lower the mixer speed and gradually add the flour mixture. Stop the mixer and add 1/3 of the meringue. With a spatula, incorporate it into the cake batter by making circular motions. Then, add another 1/3 and fold it in, followed by the remaining meringue, and incorporate it with the spatula using circular motions. Put the batter in a rectangular baking pan 23x32cm, which is buttered and floured. Bake in the preheated oven for 30 minutes.
At the same time, prepare the milk mixture: In a bowl, mix the sweetened condensed milk, evaporated milk, and regular milk. Take the warm cake out of the refrigerator and pierce it all over the surface with the back of a wooden skewer. With a spoon, pour the syrup with the three milks gradually over the cake, starting from the edges. Let the cake cool.
For the topping: We put the cream in the mixer bowl, along with the sugar and vanilla, and beat on medium speed until we have a firm meringue, about 7 minutes. We put the whipped cream on top of the cake and refrigerate for 4-5 hours or overnight to freeze. We sprinkle with the pistachios and serve.