Final answer:
The perfect shot of espresso features a rich color with a golden-brown crema, and its flavor balances sweetness, bitterness, and acidity. Quality is judged by the look of the crema and the extraction time resulting in a full-bodied shot. It differs from Viennese specialty coffee that comes with cream and sugar.
Step-by-step explanation:
The perfect shot of espresso is characterized by its rich, dark color, a thick golden-brown layer called crema on top, and a full-bodied flavor with a balance between sweetness, bitterness, and acidity. A proper espresso should be made with freshly ground coffee, tamped evenly, and extracted within 25-30 seconds to produce about 1 ounce (30 milliliters) of drink. The appearance of the shot can indicate quality; under-extraction might look watery and have thin crema, while over-extraction can result in a bitter taste and very dark crema.
In contrast to the Viennese specialty, which is a strong black coffee known as Wiener Kaffee and differs from an espresso shot due to its serving style topped with whipped cream and powdered sugar served separately, a perfect espresso prioritizes the quality of the coffee extraction itself without additional garnishes.