Preheat the oven to 450 degrees . Preheat a waffle iron. Meanwhile, in a large bowl, whisk together the flour, baking soda and 1/4 tsp. each salt and pepper. Make a well in the center, then add the eggs, EVOO and chives; whisk to break the eggs. Whisk in the buttermilk until smooth.
Spray the hot waffle iron with cooking spray. Ladle in the batter, close and cook according to manufacturer's directions until golden (make 4 waffles). Transfer the waffles to a baking sheet to cool.
Brush some mustard onto each waffle. Layer 2 waffles with a slice of cheese, 2 slices of ham and some tomato slices. Set the remaining 2 waffles on top mustard side down. Bake until toasted and the cheese is melted, about 10 minutes. Cut each sammy into 4 wedges. Serve 2 wedges per person with the pickle spears.