Place the yams, ginger and garlic in a pot and just cover with cold water. Bring to a simmer, and simmer until yams are tender, about 10 to 12 minutes.
Drain well, ensuring the ginger and garlic stay with the yams. Place in a food processor with all remaining ingredients, except mint, and purée until smooth. Add mint and pulse 20 seconds more. Thin dip with a little more olive oil or orange juice if you find it too thick.
Spoon the dip into an attractive serving bowl. Can be served warm, or cooled to room temperature, covered and refrigerated until ready to serve as a chilled dip.