Place all ingredients in a saucepan over medium high heat and stir occasionally until the agar-agar has dissolved completely or almost completely (as noted above, I could never get the flakes to completely dissolve), about 15 minutes. The mixture should remain simmering, but not come to a heavy boil.
Let the mixture stand for about 10 minutes at room temperature and pour into a silicone mold (any shape you'd like) or ramekins. I made mine in my silicone cupcake tin. I filled the molds 3/4 full and the recipe made eight.
Refrigerate until the panna cotta sets, 2-3 hours.