Panna cotta, when good, is a simple, spectacular dessert. It's also stupidly versatile—you can flavor it with anything. Tea, fruit, spices.. basically anything that you can steep into milk or puree and fold into the base. It can be instantly seasonal and is delicious year-round. This recipe is for a simple vanilla base that you can go crazy with, plus a basic coulis recipe that would work for most fruits. —Clair Gu
In a small bowl, pour in 1/2 cup of the heavy cream. Sprinkle about 2/3s of the gelatin packet over the cream and stir to combine. Let sit for 5-10 minutes. (NOTE: I prefer a softer texture and thereby don't use all of the gelatin. If you prefer a firmer texture and/or have concerns about your cream setting up, use the whole thing)
In a heavy-bottomed, medium-sized saucepan, combine the remaining cream, buttermilk, sugar, zest, and vanilla. Cook over low heat until steam rises and the sugar is completely dissolved, about 15 minutes. Your temperature should be about 180F/82C.
Add in the gelatin mixture (you should see it starting to set up by now) to the hot cream and whisk to combine, breaking any clumps. Retain the 180F/82C temperature for about 5 minutes, but DO NOT LET IT BOIL.
Remove the hot cream from heat and strain through a fine mesh sieve into 6 lightly oiled ramekins. Chill for 4 hours or until set. (NOTE: it is VERY IMPORTANT to strain this. Even the smallest clump will affect the silky texture you are going for here)
You can serve these in the moulds or unmoulded. To unmould, I've found dropping the ramekins for 30 seconds into a hot water bath about halfway up the sides of the container allows for perfect shapes and no sticking.
In a small saucepan, add the raspberries, water, and sugar. Bring to a boil and simmer for 10 minutes.
Transfer the hot berries and their syrup to a blender. Add the remaining ingredients and blend on high until well-pureed.
Strain through a fine mesh sieve and serve over unmoulded panna cotta.