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1
Marinade:.
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2
Whisk together Marinade ingredients in a small bowl, place in a zip top plastic bag; add flank steak.
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3
Seal the bag and massage the marinade all over the steak.
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4
Refrigerate for at least 3 hours, preferabley overnight.
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5
Horseradish sauce:.
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6
In a small bowl, whisk together sour cream , mayonnaise, horseradish and mustard.
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7
Season with salt and pepper to taste.
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8
Cover with plastic wrap; refrigerate while preparing steak.
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9
In a small bowl mix roasted red peppers, garlic and basil leaves, set aside.
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10
Heat broiler, if using, with rack 6 inches from heat.
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11
Remove steak from marinade; shake off excess marinade and place on a roasting pan fitted with a rack, if broiling.
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12
BBQ or broil 6 minutes on each side for medium rare.
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13
Let rest 5 minutes before slicing 1/4 inch thick against the grain.
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14
Place watercress or cilantro in a bowl; toss with oil and the lemon juice.
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15
Season with salt and pepper.
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16
Toast bread slices; place 1/4 watercress mixture on bottom slice of toast; place 1/4 of steak slices over watercress; drizzle horseradish sauce over steak; place 1/4 of roasted red pepper mixture over sauce; top with second slice of toast.
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17
Repeat for 4 sandwiches.
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18
Enjoy!