In a medium saute pan, heat the oil over medium heat.
In a small bowl, combine the wasabi powder and water to create a paste. Let sit for 5 minutes.
In a medium bowl, whisk together the flour, cornstarch, salt and beer until smooth. Working in batch, dredge a few green beans in the beer batter, then place in the hot oil. Cook for 3-4 minutes per side then remove to a paper towel lined plate to drain. Repeat until all green beans have been cooked.
Add the greek yogurt and ranch seasoning to the wasabi paste and mix well.