adapted, and made vegan, from Gourmet
1 medium red onion, finely chopped
1 chopped red bell pepper
1/2 teaspoon finely chopped fresh rosemary or basil (I used basil)
3 tablespoons extra-virgin olive oil
2 portabello mushroom caps, coarsely chopped
Handful of torn baby spinach leaves
1 1/3 cups all-purpose flour
2 teaspoons baking powder
1/2 teaspoon salt
3 1/2 tablespoons vegetable oil
1/2 cup soy milk
Cook onion, bell pepper, mushroom, rosemary or basil, a rounded 1/4 teaspoon salt, and 1/8 teaspoon pepper in oil in a heavy medium skillet over medium heat, stirring occasionally, until onion is golden, about 10 minutes. Add spinach and cook until wilted. Transfer to a bowl to cool.
Preheat oven to 400°F with rack in middle.
Whisk together flour, baking powder, and salt in a bowl. Blend in the oil with a fork or your fingertips until most of mixture resembles coarse meal with some small (roughly pea-size) lumps. Add milk and stir with a fork until a shaggy dough forms. Gently knead dough 8 to 10 times with floured hands on a lightly floured surface.
Roll out dough into a 12-inch square (1/4 inch thick) on a lightly floured surface with a floured rolling pin. Cut into 3 equal strips. Arrange strips 1 inch apart on an ungreased baking sheet and spread with filling, leaving a 1/2-inch border around edges.
Bake until crust is golden, 20 to 25 minutes. Transfer to a rack using a large metal spatula and cool to warm or room temperature. Cut crosswise into 1-inch pieces.
• Pissaladière strips can be baked 3 hours ahead and kept, uncovered, at room temperature.