If potato sandwich sounds strange to you, call it by its original name: potato smørrebrød (photo courtesy Idaho Potato Commission).
 Fingerling potatoes (photo courtesy The Cilantropist).
 The leftover fresh dill can be used in many recipes: egg, tuna and potato salads, green salads, Martinis, omelets, sauces… (photo courtesy McCormick).
In Denmark, smørrebrød (pronounced SMUHR-broht) is a slice of buttered dark rye bread covered with any manner of toppings: smoked salmon, prawns and other fish, cold cuts, cheese or spreads.
Smørre is the word for butter; brod is bread. With toppings, it becomes an open-face sandwich. We like making them to serve with tea breaks.
How about potato smørrebrød?
This recipe is from Chef Claus Meyer at Open Rye, a stand in the Great Northern Food Hall in New York City.
The recipe, made with fingerling potatoes, dill mayonnaise and a garnish of pickled pearl onions, is a Nordic favorite. Thanks to the Idaho Potato Commission for sending it to us.
RECIPE: POTATO SMØRREBRØD
While this recipe makes four open-face sandwiches that use just one pickled onion apiece, the remaining onions make delicious garnishes for other sandwiches, burgers, or just about anything, including salads.
If you want a hack, buy a jar of cocktail onions.
Ingredients For The Pickled Pearl Onions
3/4 cup sugar
1 cup apple cider vinegar
1 cup water
1/2 pound pearl onions, peeled (thawed if frozen)
Pinch of kosher salt
6 ounces Idaho fingerling potatoes
5 (3-inch) strips lemon zest
3 dill stems
1/4 teaspoon black peppercorns
Kosher salt, as needed
1/2 cup mayonnaise
2 tablespoons fresh dill, finely chopped, plus small sprigs for garnish
1 teaspoon Dijon mustard
1 teaspoon white wine vinegar
4 pickled pearl onions
Unsalted European-style butter*, softened for spreading
4 slices dense rye bread, about 3 x 4 inches each
Pepper, to taste
Garnish: shallot, very thinly sliced
Garnish: small potato chips (we used the new White Truffle Potato Chips from Trader Joe’s)
1. MAKE the pickled onions. In a medium saucepan, combine the sugar, vinegar and water and bring to a boil. Add the pearl onions and a pinch of salt. Remove from the heat and transfer to a heatproof jar; let cool completely. Refrigerate overnight or up to 5 days.
2. MAKE the potato topping. Place the potatoes, lemon zest, dill stems and peppercorns in a medium saucepan, cover with water and bring to a boil. Add a generous pinch of salt and simmer until just tender, about 20 minutes. Remove from the heat and let the potatoes cool in the cooking liquid, about 30 minutes. Drain well and discard the aromatics. Cut the potatoes into 1/4-inch-thick slices.
3. WHISK the mayonnaise with the chopped dill, mustard and vinegar in a small bowl. Season to taste with salt.
4. CUT 4 of the pickled onions in half and separate the layers (reserve the remaining onions for another use). Spread butter on the rye bread and arrange the potato slices on top. Dollop the dill mayonnaise on the potatoes and season with salt and pepper.
5. GARNISH with the pickled onion petals, sliced shallot, dill sprigs and potato chips; serve immediately. For a simpler garnish, you can use small clusters of dill leaves.
*There is also Danish-style butter, less often found in the U.S. It is unsalted, cultured butter. A culture is added to the cream and allowed to stand overnight for the acid flavor to develop before churning. Here are the different types of butter.