Yield: 4 portions
In a 12-inch skillet (preferably nonstick), heat 1 tablespoon of the oil over medium-high heat. Add mushroom caps, smooth side up; cover and cook until caps look moist, about 8 minutes. Turn caps; cover and cook until browned and tender, about 7 minutes; drain on paper towels.
Meanwhile, in a food processor container, combine feta and garlic; pulse 2 or 3 times, until chopped. Add tomatoes, basil and the remaining 4 tablespoons olive oil; pulse just until mixture is spreadable but a bit chunky.
Spread mixture on bread slices, dividing evenly. Arrange spinach leaves and mushroom caps on 4 of the bread slices; top with remaining bread.
To serve, cut sandwiches in halves.
Please note that some ingredients and brands may not be available in every store.