This is a very mildly flavored cake.
Preheat oven to 190ºC (375ºF).
Line a long, thin pan with cooking parchment. If you have a jelly roll cake pan (10½"X15½"), use that.
Prepare your ingredients. You will need 3 bowls (one for mixing the cake, one for whipping egg whites, and one for sifting the dry ingredients into). Two whisks are also handy, one for the cake, and one for the egg whites.
¾ C sugar
1 t vanilla
3 T flour
3 T cocoa powder - I prefer Van Houten
½ t cream of tartar
⅛ t salt
fine or powdered sugar (for dusting)
Separate the eggs. Put the yolks in one bowl and the whites in another.
Whip the egg yolks until light and airy. While continuing to whip, gradually add ½ C sugar and then the vanilla. Set aside.
Sift the flour, cocoa powder, and salt together into a bowl.
Gradually add the flour mixture to the egg yolk mixture. Set aside.
Whip the egg whites and cream of tartar until stiff. Add ¼ C sugar to the whites and whip until peaks form. Use a spatula to gently fold the whites into the batter. Continue folding until the batter is one color.
Gently spread the batter in your pan, and bake for 12-15 minutes, or until the cake is lightly browned and bounces back when gently touched.
Loosen the sides with a knife and gently turn the cake over onto a cooling rack. Get a tea towel, and sprinkle on it a very light layer of fine-grained sugar. Lay the cake on the sugared towel, roll it up carefully, and put it on the rack to cool.
When the cake is cooled, unroll it, remove the towel, and fill with whipped cream or chocolate whipped cream. To make that, whip the cream and then add 10-20 grams of dark chocolate that has been melted in the microwave with a little coffee liqueur or espresso, then cooled before whipping into the cream.
Re-roll the cake after filling and finish with the seam side down.
Refrigerate the cake until serving.