I love these cookies so much, sometimes I'll bake a loaf of bread just to make them. After baking, they freeze well for a month or two (though they won't last that long). Just put them in an airtight container and microwave them on high until warm and chewy.
Technique tip: The cookies should be slightly firm to the touch. To confirm that they're ready, check the bottom on one; it should be lightly browned.
Swap option: To make these less cakey, more delicate, like Florentines, reduce the flour to 1/4 cup. The recipe as written is excellent with up to 1 cup chopped dark chocolate or 1/2 cup shredded unsweetened coconut stirred in. Or reduce the butter to 1 stick and add 1/2 cup peanut butter.
Special equipment: Food processor.
Preheat the oven to 375 F. Adjust the racks so they're toward the middle of the oven with several inches in between.2.
Put the bread cubes in a food processor with the sugar and let the machine run until the mixture looks like wet sand, 1 to 2 minutes. Add the butter and let the machine run until the dough starts to form a loose ball around the blade, about a minute. Scrape down the sides of the work bowl with a rubber spatula and repeat. Add the eggs and vanilla, and let the machine run for another minute, stopping once or twice to scrape the sides again.3.
Combine the flour, baking powder and salt in a large bowl. Transfer the breadcrumb mixture to the bowl and stir until a somewhat loose dough forms.4.
Drop the dough by heaping tablespoons onto large ungreased cookie sheets. Space them about an inch apart; you should have about 24 cookies. Press the mounds down gently with your finger to flatten them.5.
Bake, switching the cookie sheets between racks and rotating them after about 10 minutes if necessary to promote even baking, until the cookies begin to brown around the edges and are slightly firm to the touch, 20 to 30 minutes. Transfer them to a wire rack to cool. They'll keep in an airtight container at room temperature for several days or frozen for weeks.