Boil: Add coconut milk and sugar to a medium saucepan and set over medium/high heat. Bring to a boil (or at least 185°F, 85°C), then whisk in agar agar. Continue boiling for 3 minutes, watching to ensure it doesn't spill over.
Vanilla: Cut the vanilla bean in half lengthwise, and use the back of your knife to scrape out the seeds. Add the seeds to the mixture, whisking well to combine.
Cool: Pour mixture into 6 individual serving bowls or ramekins (you may choose to lightly grease them if you want to serve the panna cotta out of the bowls). Set in the fridge to cool until set, about 1 hour.
Topping: Meanwhile, add raspberries, sugar, lemon, and water to a medium saucepan. Cook, uncovered, over medium heat for 10 to 15 minutes, until raspberries have broken down and mixture has thickened some.
Serve: Optionally invert the panna cotta onto plates or serve in the bowls/ramekins. Top with raspberry topping.
Panna Cotta Flavor Ideas:
Berry: Replace the raspberries with your favorite berry and cook the same way.
Mango: Use 1 cup of mango (fresh or frozen), along with the lemon, sugar listed above (not water). Optionally puree before cooking for a smoother texture.
Chocolate: Melt 3 oz (½ cup) dark chocolate, then whisk into the coconut mixture after cooking.
Lemon: After cooking the coconut mixture, remove from heat and add 3 Tbsp lemon juice and the grated zest from 2 lemons (no vanilla bean).
Strawberry: You can either do a simple strawberry topping by replacing the raspberries, or incorporate strawberries into the panna cotta itself. For the later, omit ½ cup of coconut milk. After cooking the coconut mixture, whisk in ½ cup pureed strawberries.
How to Make Vegetarian Panna Cotta with Cow's Milk Use 2 ½ cups heavy cream, ½ cup milk, and the same sugar, agar, and vanilla amounts as above. Bring the heavy cream to a boil, then add agar agar and boil for 3 minutes. Remove from heat and mix in all remaining ingredients, then pour into ramekins and cool as instructed above!