Pre-heat the oven to 425°F. Place the pan in the oven a couple minutes before you are ready to the molds with the batter.
Sift together the flour and salt into a large bowl.
Whisk together the eggs, milk, butter and pepper in a separate bowl.
Add egg mixture to flour mixture and stir with a wooden spoon until combined (okay if some lumps remain).
Take the pan from the oven and spray liberally with the cooking spray.
Using a ladle or large spoon, fill each mold just over half way with the batter.
Distributing equally, add the cheese, ham, tomatoes and chives on top of the batter in each mold.
Top with just enough batter to nearly reach the top of each mold. (You may have some batter left over).
Place in the oven and bake for exactly 15 minutes, then reduce the temperature to 350°F and bake for another 18 minutes. DO NOT OPEN THE OVEN DURING BAKING TIME.
Remove from oven and carefully take the popovers out of the molds.
Gently prick the sides of the popovers with a toothpick to allow steam to escape.
Serve at once and enjoy!