Heat oven to 300°. Combine 1 1⁄4 cups cream, sugar, rosemary, and bay leaves in a 2-qt. saucepan over medium-high until bubbles form around the edges. Remove from heat and let steep for 15 minutes; strain, discarding herbs. Return cream to pan over medium. Whisk eggs and yolks in a medium bowl until combined; gradually whisk about 1⁄4 cup of the hot cream into eggs, then stir egg mixture back into pan with hot cream. Remove from heat and strain through a fine-mesh sieve. Divide custard between eight 3-oz. espresso cups and place in a baking dish; pour boiling water into dish to come halfway up the sides of cups. Bake until custards are set but still slightly loose in center, about 30 minutes. Transfer espresso cups to a wire rack; cool. Chill until firm, at least 4 hours.
Whip remaining cream in a bowl until stiff peaks form; fold in yogurt, lemon zest, and salt. Serve custards with a dollop of yogurt cream on each.