You can serve the pickled currants in their liquid as a relish alongside sliced meats, such as ham and roast chicken.
Make the pickled currants: Put currants into a nonreactive bowl; set aside. Stir 1 1/2 cups water, the vinegar, sugar, coriander seeds, ginger, and zest in a medium pan. Bring to a boil, stirring until sugar has dissolved. Reduce heat; simmer, stirring occasionally, 10 minutes. Let cool 10 minutes. Pour through a fine sieve over currants in bowl. Stir gently to submerge currants. Let stand at least 30 minutes.
Make the dressing: Stir shallot, pickling liquid, and 1/4 teaspoon salt in a large bowl, and let stand 20 minutes. Stir in mustard. Gradually add oil, whisking constantly until emulsified. Set aside.
Make the salad: Add greens to bowl with dressing, and toss gently. Season with salt and pepper. Divide the salad among 4 serving plates, and scatter about 2 tablespoons pickled currants on each plate. Spread pate on each slice of bread; serve 2 slices with each salad.
Pickled currants will keep refrigerated in an airtight container up to 2 weeks