In Mexico, this caramelized milk is called "cajeta" and is sold in jars at the supermarket. It can be purchased from an online vendor
And, yes, authentically, it is made from goat's milk & sugar!
I have made two versions of this very popular & delicious dessert – but for both of them I simply mix the three milks together, without reducing the mixture almost to the consistency of toffee. In the first recipe, I combine sweetened condensed milk with half-and-half, evaporated milk, sour cream, and vanilla. This mixture is poured over a 10-inch round génoise cake and allowed to soak for 12 hours. Then, the cake is turned upside down, sliced, and garnished with whipped cream & fruit. (Mexican cooks occasionally cover it with meringue prior to plating it for service.)Pastel de Tres Leche
is actually native to Nicaragua, but it is also very prevalent on menus in the Dominican Republic, where it has been adapted to the tastes of the Dominicans. Influenced by the Dominican version, I make a rich cake from 1 lb. EACH butter & granulated sugar, 10 whole eggs, 1½ lbs. cake flour, ½ oz. EACH baking powder & vanilla extract, and 1 cup orange juice. The cake is baked in a ceramic bowl, perforated while slightly warm, and soaked with the triple-milk concoction (sometimes spiked with brandy).
Further to the topic of Mexican desserts, I recommend that you bake & enjoy: Capirotoda
(bread pudding) & Huevos Realas
-- "Royal Eggs," originally a Spanish dish that has been embraced by Mexican cuisine as its own.