Alfajores (Argentine Dulce de Leche Sandwich Cookies)
Cornstarch makes up a large share of the flour in these cookies, which is why they crumble so tenderly before the thick layer of dulce de leche in the middle takes over. Dulce de leche, milk cooked down slowly into caramel, has a strong toffee flavor, so the cookies themselves are kept plain. The sweet traces back to medieval Andalusia, but this round sandwich form took shape in 19th-century Argentina and Uruguay. Pulled from the oven before they color, the rounds stay pale and soft.