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1
Put a large sheet of foil on a heatproof work surface.
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2
Heat sugar in a 12-inch heavy skillet over medium heat, stirring with a fork to heat sugar evenly, until it starts to melt, then stop stirring and cook, swirling skillet occasionally so sugar melts evenly, until it is golden. Add toasted almonds, stirring until coated well, then carefully pour onto foil (mixture will spread) and cool completely, about 15 minutes. Peel praline off foil and chop with a large heavy knife. Transfer to a food processor and pulse until finely chopped.
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3
Preheat oven to 325u00b0F with racks in upper and lower thirds. Line 2 large baking sheets with parchment paper.
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4
Whisk together flour and table salt. Pulse almonds with sugar in a food processor until finely ground.
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5
Beat butter and sugar mixture with an electric mixer until pale and fluffy, then beat in egg whites and extracts. At low speed, mix in flour mixture in 3 batches until just combined well.
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6
Transfer batter to pastry bag, then dab some batter under corners of parchment to secure to baking sheets. Pipe 6-inch-long strips (about 1/3 inch wide) 1 1/2 inches apart in 2 slanted rows (so they will fit) on each baking sheet.
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7
Bake until slightly puffed but still pale, 7 to 9 minutes, then sprinkle generously with praline and lightly with sea salt. Continue baking until cookies are baked through and golden-brown on edges, 7 to 11 minutes more. (Turn baking sheets if cookies are browning unevenly.) Slide parchment with cookies onto racks to cool completely (cookies will crisp as they cool).
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8
Form and bake more cookies on cooled baking sheets lined with fresh parchment.
