Bay seniors who dream of being their own baristas might want to consider enrolling in any of the coffee classes around the city. On Wednesday March 19 Four Barrel Coffee on Valencia Street is conducting a seminar on Espresso 101 from 4-7pm where you can master the subtleties of brewing including advanced milk steaming and pouring. $175. For instruction in the intricacies of lattes there’s a workshop at the Drip’d Coffee Lab on March 29 from 4-5:30. $32.