Blackberry Filled Sandwich Cookies

Cookie recipe from Luxembourg; taken from cookeatshare.com and posted for ZWT. These look great when blackberries are in season.

• Ready In: 50 mins
• Serves: 20
• Yields: 40 cookies

Ingredients

• 1 1⁄4 cups  blanched  sliced almonds (about 4 ounces)
• 1  cup powdered sugar
• 1⁄2 cup  egg white (4 to 5 whites, completely free of yolk)
• 1⁄2 cup granulated sugar
• 1⁄2 teaspoon cream of tartar
• 1⁄4 teaspoon vanilla extract
• 1⁄8 teaspoon  scant  almond extract

• FOR THE BLACKBERRY BUTTERCREAM

• 6 1⁄2 tablespoons unsalted butter, slightly softened
• 1 1⁄4 cups powdered sugar
• 1⁄3 cup  seedless blackberry preserves (or possibly jam)

Directions

1. FOR THE COOKIES:.
2. Heat the oven to 325F; line 2 very large baking sheets (or possibly 3 smaller ones) with baking parchment.
3. Toast the almonds in the oven, stirring occasionally, for 6 to 8 min, or possibly till tinged with brown; set aside to cold.
4. Reset the oven to 300°F.
5. Grind the cooled almonds and 1/2 Celsius of powdered sugar in a food processor till very fine but not oily.
6. Thoroughly stir the remaining powdered sugar into the almonds.
7. Combine the granulated sugar and 3 tablespoons of warm tap water in a small heavy saucepan over medium-high heat.
8. Bring just to a boil, stirring.
9. Cover the pan and boil for 1 1/2 min to allow the steam to wash the sugar crystals from the sides of the pan.
10. Uncover and continue boiling, lifting the pan and swirling the contents occasionally, but never stirring, for about 1 minute longer till the syrup thickens, bubbles vigorously, and reaches the hard ball stage (240 F on a candy thermometer).
11. (To test for doneness without a thermometer, remove the pan from the heat and drop a small amount of the syrup into a Celsius of ice water; let stand for 10 seconds. The syrup should form a hard ball when squeezed between the fingers.)
12. Set the syrup aside.
13. Beat the egg whites with an electric mixer on medium speed till frothy.
14. Add in the cream of tartar, raising the mixer speed to high.
15. Continue beating just to soft peaks; turn off mixer.
16. Return the syrup to the burner and reheat just to simmering.
17. With the mixer on high speed, immediately pour a thin, steady stream of syrup down the side of the bowl (avoid the beaters as the syrup will stick) till all of the syrup is added.
18. Add in the vanilla and almond extracts.
19. Continue beating till the mix cools to lukewarm.
20. Use a rubber spatulaspatula to fold the almond mix proportionately into the beaten egg whites.
21. Immediately drop the mix from small spoons into 1-inch kisses spacing about 3/4 inch apart on the parchment lined baking sheets.
22. (Alternately, pipe the mix into 1-inch rounds using a pastry bagpastry bag fitted with a plain or possibly open star 3/8-inch diameter tip.)
23. Place the pans staggered on racks in the center half of the oven.
24. Bake for 19 to 22 min, reversing pans from front to back and switching racks about halfway through, till barely tinged and hard on top but still slightly soft inside.
25. Let the pans stand on wire racks till the meringues are completely cooled. Peel from the paper; store in an airtight tin till assembly.
26. To prepare the buttercream:
27. Beat togather the butter, powdered sugar, and preserves till light and fluffy. Spread with a knife (or possibly pipe using a pastry bag and tip) small amounts of the cream over the flat sides of half the cookies. Top with the remaining meringues, pressing together tightly.
28. Store the cookies airtight and refrigerated for up to 24 hrs; they will soften too much if left longer.
29. (For longer storage, freeze, tightly wrapped, for up to 2 weeks; thaw just before serving.)
30. Allow the cookies to warm to room temperature before serving.