Yes, but the instructions will be slightly different as agar agar dissolves and activates at a much higher temperature than gelatine. It is also much stronger than gelatine, so you will need a much smaller quantity of agar agar. Bring the coffee cream mixture to a boil and add 1/2 to 3/4 teaspoon agar agar powder (depending on the texture you want). Whisk well for a couple of minutes over medium heat, then pour directly into the serving cups. Agar will start to set as soon as the temperature drops so make sure to be quick.