4 ounces light cream cheese, room temperature
3 tablespoons butter, divided
3/4 cup plus 1 teaspoon all-purpose flour, divided
8 ounces fresh mushrooms, coarsely chopped
1/2 cup chopped green onions
1/4 cup dried thyme leaves
1/2 cup shredded Swiss cheese
Place cream cheese and 2 tablespoons butter in bowl of electric stand mixer. Attach flat beater to mixer. Turn to medium and beat for 1 minute. Stop and scrape bowl. Add 3⁄4 cup flour. Turn to low and mix for 1 minute, or until well blended. Form mixture into ball. Wrap in waxed paper and refrigerate for 1 hour.
Clean mixer bowl and beater.
Divide chilled dough into 24 pieces. Press each piece into lightly greased miniature muffin cups, forming a pastry shell.
Melt remaining butter in 10-inch skillet over medium heat. Add mushrooms and green onions. Cook and stir until tender. Remove from heat and set aside to cool slightly.
Place egg, remaining flour and thyme in mixer bowl. Turn to medium-high and beat for 30 seconds. Blend in cheese and cooled mushroom mixture.
Spoon egg mixture into pastry-lined muffin cups. Bake at 375°F for 15 to 20 minutes, or until egg mixture is puffed and golden brown. Serve warm. Yields 24 tartlets.