How to Make It
Heat a medium nonstick skillet over medium-high heat. Add oil to pan; swirl to coat. Add shallots, garlic, mushrooms, and thyme; sauté 7 minutes or until mushrooms are browned. Add spinach; sauté 4 minutes or until liquid almost evaporates. Remove mixture from pan; discard thyme sprig. Wipe pan clean.
Combine 1/4 teaspoon salt, 1/8 teaspoon pepper, and 4 eggs in a small bowl, stirring with a whisk. Return pan to medium heat. Add 1 1/2 teaspoons butter; swirl to coat. Add egg mixture; cook 1 minute. Lift edges of omelet with a rubber spatula, tilting pan to roll uncooked egg onto bottom of pan. Cook 1 minute or until center just begins to set but is still very soft. Arrange half of mushroom mixture over middle of omelet; sprinkle with 1/4 teaspoon salt and 1/8 teaspoon pepper. Run spatula around edges and under omelet to loosen from the pan; fold in half. Slide omelet onto a plate. Repeat procedure with remaining ingredients. Cut omelets in half.