Beat the yolks with 5 tbsp (75 ml) of the sugar 3-4 minutes, until mixture is creamy and thickened.
Add melted butter, whisking to combine.
Sift flour over yolk mixture. Whisk to combine.
Beat egg whites until foamy and add the remaining 1 tbsp (15 ml) of sugar. Continue beating until stiff peaks form, but the mixture shouldn’t be dry. Add beaten whites to yolk mixture, folding delicately. Do not stir too much.
Spread mixture on baking sheet and cook in centre of oven 6-8 minutes, or until cake is set and the tip of a knife comes out clean. Use a paring knife to loosen edges of cake from pan. Turn cake onto a damp cloth, remove parchment paper, and immediately roll up into the towel lengthwise to form a long and thin cylinder. Let it cool to room temperature.
In a small saucepan, put sherry and jam over moderate heat until liquefied. Remove from heat.
Unroll the cake and spread the warm jam on its entire surface. Top one side (width-wise) of the cake with the sliced Brie and roll back width-wise into a log shape. Sprinkle top of log with icing sugar and slice into ½” (1 cm) pinwheels.
Serve immediately or refrigerate.