As more ingredients, such as sugar, became available, culinary utensils improved and techniques such as leavening with egg whites developed, cakes became more and more elaborate. Overtime, the discipline of confectionery developed and by the 15th century, cakes became ornate, multi-layer showpieces decorated with marzipan and sugar sculptures; the appearance of a cake was just as important as its flavour. However, these elaborate cakes, which possessed many aspects of contemporary cakes (such as layers and decorations), were only available to the very wealthy. In modern times, with the wide availability of materials, cookbooks and utensils such as electric beaters, professionals are no longer required to produce elaborate birthday cakes. Today birthday cakes are not only served to celebrate human birthdays, but also to commemorate important anniversaries, such as a country's birthday.
The contemporary commercially produced North American birthday cake is usually a multi-layer affair, each layer separated with various fillings, usually covered with icing. A birthday greeting is often added to the top of the cake. The variations on the birthday cake are enormous; cakes can be chemically leavened, or leavened with beaten egg whites; they can be round or rectangular - in short, there is no common form.
The service of a birthday cake is often preceded by the singing of Happy Birthday to You in English speaking countries, or an equivalent birthday song. In fact, the phrase "Happy Birthday" did not appear on birthday cakes until the song Happy Birthday to You was popularized in the early 1900s. Variations on birthday song rituals exist. For example, in New Zealand, the Happy Birthday to You is sung out of tune and is followed by clapping, once for each year of the persons life and once more for good luck. In Uruguay, party guests touch the birthday person's shoulder or head following the singing of Happy Birthday to You.
The birthday cake is often decorated with taper candles which are secured with special holders. In North America, the number of candles is equal to the age of the individual whose birthday it is. Traditionally the birthday person makes a private wish, which will be realized if all the candles are extinguished in a single breath.
In medieval England, tokens, such as coins and thimbles, were baked inside the birthday cake, a tradition which persists today with the Christmas pudding. Receiving a coin in one's slice predicted future wealth while it was believed that those receiving a thimble would never wed.
Though the exact origin and significance of the candle blowing ritual is unknown, the history of placing candles on top of the cake is well documented. This tradition can be traced to Kinderfest (Kinder is the German word for 'children'), an 18th century German birthday celebration for children. A letter written in 1799 by Goethe recounts: "...when it was time for dessert, the prince's entire livery...carried a generous-size torte with colorful flaming candles - amounting to some fifty candles - that began to melt and threatened to burn down, instead of there being enough room for candles indicating upcoming years, as is the case with children's festivities of this kind...". As the excerpt indicates, the tradition at the time was to place candles for each of the individual's life with some added candles 'indicating upcoming years'. Candles, being slow-burning, are believed to be symbolic of the passage of time. In fact, they were often used as timekeepers. The origin of birthday cake candles can be further traced back to the 16th century German tradition of placing tapers on Christmas trees. This tradition was brought to North America by German immigrants. By 1927, the Sears Roebuck catalogue offered birthday candles and holders for sale .