Whole poppy seeds are widely used as a spice and decoration in and on top of many baked goods and pastries. In North America they are used in and on many food items such as poppyseed muffins, rusk, bagels, bialys, and cakes such as sponge cake. Poppy seeds can also be used like sesame seeds, added to hamburger buns or to make a bar of candy. The bars are made from boiled seeds mixed with sugar or with honey. This is especially common in the Balkans, Greece and even in the cuisines of former Austro-Hungarian countries.
The color of poppy seeds is important in some uses. According to The Joy of Cooking, “the most desirable come from Holland and are a slate-blue color.”
When used as a thickener in some dishes, white poppy seeds are preferred, having less impact on the color of the food. In other dishes, black poppy seeds are preferred, for maximum impact. Blue poppy seeds are used in various German breads and desserts as well as in Polish cuisine.