2 tbsp (30 mL) mayonnaise
1 tsp (5 mL) horseradish
2 green onions, thinly sliced
1/4 tsp (1 mL) ground pepper
2 oz (57 g) butter
4 slices sourdough bread (1/2 inch / 1.25 cm thick)
4 leaves Boston lettuce
8 oz (250 g) cooked roast beef, sliced
2 oz (57 g) aged white cheddar, sliced
In a small bowl, combine mayonnaise and horseradish; add onion and mix well. Finish with pepper. Refrigerate.
Butter each slice of bread on one side and grill until golden brown. Remove from heat. Spread horseradish mayo on the non-grilled side of one slice of bread, and place two leaves of lettuce on the non-grilled side of the other. Top lettuce with half the roast beef and cheddar; put both halves of sandwich together; repeat.