Generously butter or grease the shell portions of the madeleine pans. In a small saucepan, melt the butter over medium heat, browning it lightly for extra flavor. In a food processor, pulse the almonds and sugar together until the almonds are ground. Don't over process or they will turn to nut butter. Place the sugar-almond mixture in a medium bowl. Or, grind the nuts in a hand grinder or blender and mix with the sugar in a medium bowl.

Using a wooden spoon, stir the flour and salt into the almond-sugar mixture. Whisk in the egg whites and almond extract and blend well. Slowly add the melted butter while stirring the batter with the whisk. Transfer the batter to a glass measuring cup or a small pitcher and pour the batter directly into each shell, filling each three-fourths full.

Bake in the center of the oven for about 12 to 15 minutes, or until well browned around the edges. Let cool in the pans for 1 or 2 minutes, then turn the pans over a wire rack to release the madeleines to cool completely.

Store in an airtight container. Well-wrapped madeleines may be frozen.