1. Preheat oven to 450 degrees.
2. Trim ends and dark green parts of the leeks, reserving only the white and pale green parts. Quarter leeks lengthwise, rinse thoroughly under cold water to remove dirt, then finely chop. Heat 1 tablespoon of the oil in large nonstick skillet over medium heat and add leeks; cover pan.
3. Spray a 9-inch pie pan with vegetable cooking spray. Sprinkle bottom with panko crumbs, then drizzle with remaining 1/2 tablespoon oil. Stir to coat the crumbs evenly, then spread crumbs over bottom of pan. Bake for 4 to 5 minutes, just until crumbs start to turn golden. Remove pan from oven but leave oven on.
4. While crumbs toast, add mushrooms to leeks. Stir in rub, cumin, and pepper. Add broth, wine, or water and stir to mix well. Cover and cook over medium-high heat until mushrooms begin to release their liquid, about 5 minutes.
5. While vegetables cook, whisk eggs and egg whites in a medium bowl. Grate the Gruyere into the eggs and mix.
6. Remove cover from vegetables and raise heat to medium high. Cook an additional 2 to 3 minutes, until most of the liquid has evaporated. Spread leek-mushroom mixture evenly on top of the toasted crumbs in the pie pan. Pour egg mixture on top and spread evenly if needed. Bake 8 to 10 minutes, until the center is firm.
7. Let tart rest for 1 minute, then cut into wedges and serve.
Source: Hannaford fresh Magazine, January - February 2012