Mix all ingredients except for flour with purple yam in stand mixer with dough hook attachment to combine, then add flour gradually, mix well over low speed for about 2 minutes, scraping sides as needed, or until dough has fully mixed and forms ball.

Wrap dough fully with plastic wrap, rest (chilled) for at least 4 hours and up to 36 hours.

Divide yam dough into portions, roll into balls, flatten on rice floured work table, roll with pin into circle shapes, cut with ring cutter.

Grill to toast and lightly char.