Heat the oven to 350 degrees Fahrenheit.
Line a large baking tray (12 x 16) with parchment paper.
Separate the egg whites and yolks in two medium bowls.
Mix half a cup of sugar and half a teaspoon of vanilla with the egg yolk.
Sift flour with baking powder or mix together. Stir the flour with the egg yolk and sugar mixture.
Beat egg whites on high speed until stiff peaks form (about 2-3 minutes). Add the egg whites to the rest of the mixture until well combined.
Bake at 350°F for 12-15 minutes or until surface is golden. Remove the cake from the pan and immediately remove the parchment paper. Cool to room temperature. Once cool, cut the cake into small cubes.
In the bowl of an electric mixer, add crumbled crackers, 8 oz tub of cold whisk, 3/4 cup prepared poppy seeds and 3/4 cup walnuts (optional) and blend 1-2 minutes on low speed.
Roll into balls no more than 3/4 inch in diameter.
Melt the chocolate in the microwave or on the stove until just melted, but not too watery or else it won't dip well (you can refrigerate it to thicken if you heat it too much). Dip the cake balls, put them on lined parchment paper and place in the refrigerator until the chocolate hardens.
Melt white chocolate and pipe slices over balls.
Store the chocolate balls in the refrigerator until ready to eat.