How to Make It
Combine first 3 ingredients (through olive oil) in a small bowl, stirring with a whisk.
Cut bread in half lengthwise; cut each half into 8 (2 1/2-inch-thick) slices. Spread mustard mixture evenly over bottom halves. Slice pickles into 2-inch pieces. Divide pickles, ham, cheese, and spinach evenly among bottom halves of bread; top with remaining bread halves. Lightly coat sandwiches with cooking spray.
Heat a large skillet over medium heat. Add 4 sandwiches to pan; place a cast-iron or other heavy skillet on top of sandwiches. Press gently, and cook 2 minutes on each side or until sandwiches are golden brown and cheese is melted. Repeat procedure with remaining sandwiches.