Grease the ramekins or muffin tin. Rinse the spinach and blanch in boiling salt water. Drain the spinach, rinse in cold water, drain and squeeze. Mash the spinach finely.
Mix the flour, spices, baking powder and baking soda. Whisk the egg, yogurt, spinach, herbs and butter. Add the flour mixture and quickly stir into a smooth batter.
Pour the batter into the ramekins or muffin tin. Bake for 25-30 minutes at 180°C (approximately 350°F). Remove from the oven and cool slighly. Remove from the pan and cool on a wire rack.
Serve the muffins on tomato slices and garnished with blanched asparagus tips and chervil.