INGREDIENTS
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All-purpose flour, for rolling
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1 sheet frozen puff pastry, thawed
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1 tablespoon sour cream
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1 teaspoon grainy mustard
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Coarse salt and ground pepper
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2 large leeks, white and light-green parts only
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1 tablespoon unsalted butter
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3/4 pound grape or cherry tomatoes, halved if large, or plum or beefsteak tomatoes, sliced 1/4 inch thick, or a combination
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2 ounces fresh goat cheese, crumbled
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2 teaspoons fresh thyme or basil leaves