3/4 cup all-purpose flour
1 teaspoon white sugar
1 pinch salt
1/3 cup margarine
3 tablespoons cold water, or as needed

1 tablespoon olive oil
2 bunches watercress, stems removed
2 cloves garlic, crushed
1/3 cup chopped green onion
1 1/2 cups grated Parmesan cheese
5 tablespoons plain yogurt
1 teaspoon cayenne pepper