In a small saucepan, combine the mango with the mango nectar, honey, and habanero. Bring to a simmer and cook over moderate heat, stirring occasionally, until the mango is very soft, about 10 minutes. Transfer to a food processor and puree until smooth. Strain into a small bowl and let cool, about 30 minutes.

Wipe out the food processor. Add the cooled mango puree with the butter, cilantro, and salt and puree until smooth. Scrape into a bowl, cover, and refrigerate until chilled, about 30 minutes.

Light a grill or preheat a grill pan. Pull the corn husks down to the base of the stalks, leaving them attached, and discard the silk. Using butcher string, tie back the husks. Submerge the corn in a large bowl of cold, salted water for 10 minutes.

Drain the corn but do not pat dry. Grill over moderate heat, turning occasionally, until tender and browned in spots, about 8 minutes. Transfer to plates, spread with the mango-habanero butter, and serve.