nsalted butter</li>
<li>1  white onion</li>
<li>1 (5-ounce) piece horseradish (2 to 3 inches)</li>
<li>2 tablespoons buttermilk</li>
<li>kosher salt</li>
<li>4  Pain de Mie Buns or 8 slices soft slab bread</li>
<li>16 to 24  dill pickle slices</li>
</ul>
    
    <div class="recipe-header">Directions</div>
<ol class="recipe-directions">
<li>Chill the steak in the freezer until firm to the touch but not frozen, 15 to 20 minutes. Cut the steak into 1⁄4-inch-thick slices, then slice into 1⁄4-inch-thick str