In a nonstick skillet, cook mushrooms over medium heat until reduced in size and starting to brown, 8-10 minutes, stirring occasionally. Add almonds, onion and garlic; cook until nuts are toasted and fragrant, 1-2 minutes. Transfer mixture to a blender or food processor. Add oil, salt and pepper; process until smooth. Set aside.
Meanwhile, heat butter in same skillet over medium heat. Pour in eggs; cook and stir until eggs are thickened and no liquid egg remains. Divide mushroom puree among tortillas; top with eggs and, if desired, tarragon. Serve immediately.