Preheat oven to 300°F and line two baking sheets with parchment paper.
Combine ground almonds and confectioners’ sugar until very fine in a food processor.
In a medium bowl whisk egg whites until stiff but not dry. Add sugar, and whisk again until very stiff. Using a rubber spatula, add one-third almond mixture to egg whites and gently fold in, leaving some streaks. Gently fold in remaining almond mixture by thirds.
Make a piping bag for the batter: Place a sturdy plastic storage bag into a tall water glass, folding its top back around the rim of the glass. Spoon batter gently into plastic bag. Remove bag from water glass and close, snipping a hole in one bottom corner. Use this piping bag to pipe 1-inch kisses onto baking sheets. Bake 18 to 20 minutes, turning pans halfway through baking or until set but not dried out.
Let cookies cool completely, then remove from parchment paper with a small offset spatula. Sandwich cookies together with buttercream and serve, or store airtight for up to 2 days.
Using a mixer, beat butter with a pinch of salt until fluffy. Add confectioners’ sugar, jelly and vanilla extract, and beat until blended. Store covered and refrigerated, and let come to room temperature before using.
Per serving: 125 calories, 14 mg cholesterol, 7.6 g total fat, 2.9 g monounsaturated fat, 0.8 g polyunsaturated fat, 3.4 g saturated fat, 0.5 g fibre, 15 mg calcium, 15 mg magnesium, 11 mg sodium, 52 mg potassium, 1.5 mg vitamin E