Ingredients
For the horseradish sauce:
1/2 cup good-quality sour cream
1 tablespoon prepared horseradish
2 tablespoons unsweetened all-natural applesauce
2 tablespoons panko or plain breadcrumbs
2 tablespoons chives, finely chopped
Salt and coarse black pepper
For the sandwich fixin's:
8 slices white bread or peasant bread from a large round loaf
8 slices rare roast beef or about 2/3-3/4 pound thinly sliced leftover steaks of any cut
1/4 cup red onion, minced or 1 large shallot, finely chopped
A handful of flat leaf parsley, very finely chopped
1 small red chili pepper, such as Fresno or cherry, seeded and finely chopped
Zest of 1 lemon
1 small bunch watercress, trimmed, cleaned and dried
1/2 pound brick of the sharpest white cheddar available to you, thinly sliced (it’ll be crumbly if it’s very sharp)
Directions
Combine the sauce ingredients. Heat a panini press, cast iron skillet or griddle over medium to medium-high heat.
On a work surface, spread the horseradish sauce liberally over four slices of bread. Arrange two slices of rare roast beef over the sauce. Combine the red onion (or shallot) with the parsley, chili pepper and lemon zest and sprinkle liberally over the roast beef. Arrange a layer of watercress over the beef. Divide the cheese evenly among the sandwiches and set the remaining bread slices in place. Press the panini two at a time on the panini press or in a hot skillet with a pan weighted on top.