Laskey Lemon Soda with Bay Ice Cubes

To make the lemon soda concentrate, combine the zest and sugar in a mortar and crush with a pestle until fragrant, moist, and tinted yellow. Transfer the mixture to a small pitcher or lidded container and pour in the lemon juice and water. Stir until the sugar dissolves. Cover and refrigerate, agitating the mixture from time to time, until cold and infused with lemon flavor, about 2 hours. To make the ice cubes, combine the water, sugar, and bay leaves in a small saucepan and bring to a boil, stirring to help the sugar dissolve. Boil for 1 minute, remove from the heat, and let stand for 20 to 30 minutes. Strain the infused water through a fine-mesh sieve set over a liquid measuring cup. Pour into ice cube molds, and freeze until solid, about 2 hours. To serve, place 3 to 5 ice cubes in each of eight 8-ounce drinking glasses, and then add 3 tablespoons (or more, to taste) of lemon concentrate per drink. Pour in 1/2 cup (4. 3 oz / 120 g) of the sparkling water per serving and stir gently. Serve immediately.