amelcochar

Literally to thicken something into the consistency of melcocha (a taffy-like candy), used for syrups and caramel — and, informally in parts of Latin America, figuratively to fall head over heels in love, as if turned soft and sticky.

• Dejaron hervir el azúcar hasta que se amelcochó. — They let the sugar boil until it thickened into taffy.
• Se amelcochó apenas la vio entrar por la puerta. — He fell head over heels the moment he saw her walk in.
• El caramelo se amelcocha si se cocina a fuego lento. — The caramel thickens up if it's cooked over low heat.

Assuming amelcochar is only culinary — the romantic, informal sense ('to go soft/gooey over someone') is common enough in casual speech in some regions that context alone tells you which is meant.