Whatever filling you use, spread it the center of the circle. My favorite filling is Apricot Walnut (1 cup of apricot jam and 1/2 cup finely chopped walnuts). My wife prefers Raspberry Raisin Rugelach (1 cup of raspberry jam and 1/2 cup raisins). And my children prefer Chocolate Rugelach, which can be made most simply by sprinkling grated chocolate and a bit of sugar.