INGREDIENTS
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3 tablespoons unsalted butter
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1 onion, chopped
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Kosher salt and black pepper
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6 cups low-sodium vegetable broth
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10 ounces frozen peas
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1 large head romaine (1 pound), chopped
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1/4 cup fresh tarragon or mint
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2 ciabatta rolls, split
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4 slices deli ham
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4 ounces Cheddar, grated (about 1 cup)