What Pastel de tres leches means
Pastel de tres leches is a Mexican sweet name of Spanish origin meaning "three-milks cake". It is built from Spanish pastel (cake) and de (of) and tres (three) and leches (milks). It is pronounced pahs-TEL deh tres LEH-ches, and it is most associated with the whole country.
The three are evaporated milk, condensed milk and cream. Which country invented it is argued between Mexico and Nicaragua, and condensed-milk tins carrying the recipe are the likeliest reason it appeared across Latin America at once.
This is a site about what Mexican words mean, so there is no recipe here. For the name itself: From colonial convent sweets like ate and jamoncillo to the chili-and-tamarind candies of the modern corner shop. Alegría means "joy", borrachito means "little drunk one", and muégano's name is a mystery even to Mexicans.
