(I have some of the proportions written down elsewhere. When I find them I'll add them.)
Two nine inch circles of puff pastry. Preferably homemade. (It's kinda hard to describe how to make it, but it's relatively easy to do. Pictures can be found here, but they only have part of the process. If you have questions, ask them in the comments, and I'll fill in details.)
1 egg (plus 1 for egg wash.)
5 tbsp butter
1/2? cup ground pistachios (with the skin removed).
Scant cap-full vanilla
Zest of 1 lemon
Scant tbsp 151, or other light rum. (I'm curious whether Absinthe would work better, but probably with the tarragon, it would just be redundant.)
Raspberries (Enough to make there be lots or raspberries in the filling.)
About 2 bunches fresh tarragon leaves
For the filling: In a mixer with the paddle attachment, cream butter and sugar till fluffy. Chop the tarragon and lemon zest and add, together with all the other ingredients, except the raspberries, and mix till well blended. Remove from the mixer and carefully stir in the raspberries, by hand, being careful they remain intact. (You want a nut filling with raspberries in it, not a nut-raspberry mixture.)
Cover and place in a freezer (or refrigerator) till hard.
Lay out one circle of puff pastry, place the filling on top, leaving edges free from filling so another layer of puff pastry can be added on top (make the edges an inch or so wide). Moisten the edges of the pastry so it will adhere to the other piece. Place the other piece of pastry over the top, sealing it well to the bottom. (Use water, and also, press down on it well.) With the tip of a knife, cut a small slit in the center and press out any air trapped inside.
Do ahead note: At this point it can be refrigerated, covered, for a day or so.
Paint on an egg wash, place a tinfoil cone in the hole on top, paint on another layer of egg. Cut a design in the top, if desired. Bake at 450F for about 20 minutes, till pastry has risen and browned slightly. Reduce heat to 400, and cook for about 25-30 more minutes, till sides are crisp and well browned. Remove from oven, sprinkle with confectioners sugar. Melt the sugar into a glossy glaze by placing Pithiviers under the broiler, or in a 500F oven, for a few minutes, checking often, and rotating, to keep from burning.
It can be eaten almost immediately, but will also keep for several hours.
Ready to cook.
Just about finished.