1 cup apple cider vinegar
3/4 cup (packed) light brown sugar
1 small onion, finely chopped
1/4 cup coarse-grain mustard
Grated zest of 1 orange
4 Anjou pears, peeled, cored and coarsely chopped
1 large loaf focaccia (about 17 x 6 x 1 1/2 inches)
1 pound honey-glazed ham, cut into slices
8 ounces sliced Swiss cheese
3 ounces fresh baby spinach leaves (about 3 cups)
1 tablespoon butter, at room temperature
The chutney can be made up to 1 week ahead, covered and refrigerated.
Combine the vinegar, brown sugar, onion, mustard, and orange zest in a heavy saucepan, and bring to a boil over medium heat. Then reduce the heat and simmer for about 20 minutes, or until the onions are tender and the liquid has thickened slightly.
Add the pears and continue simmering gently for about 30 minutes, or until the pears soften and the liquid thickens some more. Let the chutney cool, and then keep it in the refrigerator in an airtight container. (The chutney will keep for up to a week).
Position an oven rack 8-inches from the heat source and preheat the broiler. Cut the bread in half horizontally and arrange the halves, cut side up, on 2 baking sheets. Place the ham and cheese over one of the bread halves. Toast both bread halves under the broiler for 2 minutes, or until the cheese melts and the uncovered bread is golden brown.
Scatter the spinach over the ham and cheese. Spoon the chutney over the spinach. Topwith the second bread half. Brush the top of the slider with butter and broil for 1 minute, or until the top is crisp. Cut the slider into 12 pieces, and serve.