2 teaspoons canola oil
2 teaspoons canola oil
1 teaspoon yellow mustard seeds
1 small white onion, finely diced
2/3 cup sugar
1/3 cup white wine vinegar
1 teaspoon finely chopped peeled fresh ginger
1/4 teaspoon dried red chili flakes
4 firm but ripe nectarines (about 1 1/2 pounds total), pitted, cut into about 1-inch pieces
1/2 teaspoon salt
1 ciabatta loaf (about 12 inches long by 4 1/2 inches wide)
Olive oil, for brushing
Salt and freshly ground black pepper
1 large garlic clove
3 tablespoons Dijon mustard
One 8-ounce piece Gruyère cheese, rind trimmed, cheese grated (about 2 cups)
One 4-ounce wedge St. Andre cheese, rind trimmed
1 cup baby arugula
The nectarine chutney can be made 2 days ahead, covered and refrigerated.
Heat a large heavy saucepan over medium heat. Add the oil, and then the mustard seeds and sauté until they begin to pop, about 30 seconds. Add the onion and sauté until tender and translucent, about 4 minutes. Stir in the sugar, vinegar, ginger, and chili flakes. Simmer until the sugar dissolves.
Add the nectarines and cook until the nectarines are tender but still hold their shape and the syrup thickens slightly, stirring occasionally, about 10 minutes. Stir in the salt.
Preheat the barbecue for medium heat.
Using a large serrated knife, cut the ciabatta horizontally in half leaving one long side attached, if possible. Lightly brush the cut sides of the ciabatta with olive oil and season lightly with salt and pepper. Rub the cut sides of the ciabatta with the garlic clove.
Place the ciabatta, oiled side down, on the grill and cook until just barely golden brown, rotating but not turning over to toast evenly, about 3 minutes. Remove the ciabatta from the grill and reduce the heat of one burner to low.
Spread the toasted side of the bottom ciabatta piece with the mustard. Spoon 1 cup of the chutney over the other toasted side (reserve any remaining chutney for another use). Scatter half of the Gruyère cheese evenly over the mustard. Tear off pieces of the St. Andre cheese and scatter it over the Gruyère, then scatter the remaining Gruyère cheese over. Cover with the top half of the ciabatta, chutney side down, and press firmly to hold the sandwich together. Lightly brush the top of the sandwich with oil.
Place the sandwich, oiled side down, on the grill over the burner on low heat, then brush the top of the sandwich with oil. Close the hood and grill until the cheese melts and the bread is golden brown, rotating the sandwich as needed to brown evenly, about 8 minutes per side.
Transfer the sandwich to a cutting board. Open the sandwich and scatter the arugula over the cheese. Close the sandwich. Using the serrated knife cut the sandwich into 8 pieces and serve.