Help! Does anyone have a recipe/advice on subbing agar for gelatin in a buttermilk panna cotta recipe??

I found this recipe for vegetarian Panna Cotta: https://revisfoodography.com/2015/07/strawberry-panna-cotta/

Looks like they are using 1 tsp agar agar powder to 2.5 cups of milk/cream. I would start with that.