Kasha Knishes

Ingredients

• 1½ cups dry whole kasha groats (toasted buckwheat)
• 1½ medium yellow onion, diced
• 2 teaspoons olive oil
• 2 tablespoons butter
• 2 Yukon Gold potatoes, peeled and cut into 1-inch pieces
• 2 ¾ cups all-purpose flour
• 1 teaspoon salt
• 1 teaspoon baking powder
• 1½ teaspoon apple cider vinegar
• 1 large egg, beaten
• ½ cup canola oil
• ½ cup tepid water
• 1 egg, lightly beaten, for egg wash