Step 1In a saute pan over medium heat, sweat the apples until they start to become tender, stirring frequently, 4 to 6 minutes. Stir in the dried apricots and raisins, the cider vinegar, orange zest and juice, cinnamon stick and brown sugar, and cook, stirring frequently, until the mixture begins to break down and takes on a deep, golden brown color, about 20 minutes. Remove from heat and stir in the mustard. Cool to room temperature. This makes a generous 2 cups mostarda, which will keep, covered and refrigerated, up to 1 week.
Step 1On the bottom half of each baguette section, place half of the turkey. Top the turkey with the cheese slices, then lightly drizzle over a little olive oil. Toast the open sandwiches until crisp and lightly golden, 2 to 6 minutes, depending on the heat of the toaster or oven.
Step 2Spoon a generous amount of the mostarda over the melted cheese, then top with the arugula. Spread 1 tablespoon mayonnaise over each toasted baguette top, then invert each top over the rest of the sandwiches to assemble. Serve immediately.