In a large bowl, put 1/2 cup matza meal. Beat egg yolks with 1/2 cup sugar, add to matza meal. In seperate bowl, beat the egg whites with the cream of tartar, adding more tartar if needed to soft peaks. Slowly pour the mix into the bowl with the egg whites, and stir. Add walnuts. Pour the mix into the cookie sheet and bake for 1/2 hour until done.
Remove from the oven. Put powdered sugar on a moist towel(not too wet though), and jelly roll cake while still hot.
Mix whipping cream and coffee powder, adding powdered sugar to taste, whip till stiff.
Open towel, CAREFULLY. Spread 1/2 of the mocha Whipped cream mixture all over the cake and roll back up without the towel this time and put on a platter with reserved whipped cream topping. Decorate with walnuts. Freeze.
When frozen, it tastes like ice-cream. This may be refrigerated.