Potato Knishes

1. To make Filling: Cover potatoes with water in saucepan, bring to a boil, and cook 10 to 15 minutes, or until very soft. Drain, reserve cooking liquid, and transfer potatoes to medium bowl. Mash with 1/4 cup cooking water and flaxseeds. Set aside.

2. Heat oil in large skillet over medium heat. Add onions, and cook 7 to 10 minutes, or until golden. Add spinach, garlic, and 1/2 cup potato cooking water; cook 5 minutes, or until spinach is tender and bright green and liquid has evaporated.

3. Stir onion mixture into potatoes, adding more potato cooking water, if necessary. Season with salt and pepper, if desired. Cool.

4. To make Dough: Whisk together flour and salt in medium bowl. Whisk together flaxseeds and 1/2 cup hot potato cooking water in small bowl. Whisk in oil, vinegar, and grated onion. Stir liquid into flour mixture until soft dough forms, adding 1 to 2 Tbs. more potato cooking water, if necessary. Cover with kitchen towel, and let rest 1 hour.

5. Preheat oven to 350°F. Coat baking sheet with cooking spray.

6. Divide Dough into two rounds. Roll one round of Dough into 10-inch square on well-floured work surface, then cut into four 5-inch squares. (Note: Dough is very forgiving, but it will be soft.)

7. Scoop 1/2 cup cooled Filling into center of each square. Pull Dough edges up and around Filling, and pinch to close. Place seam side down on prepared baking sheet. Repeat with remaining Dough round and Filling. Brush knishes with oil, and sprinkle with coarse salt (if using). Bake 30 to 40 minutes, or until golden brown.