Heat oven to 400°F. Place asparagus spears on baking sheet; drizzle with 2 teaspoons olive oil; toss to completely coat and bake 15 minutes or until tender but crisp. Sprinkle with sea salt and cut into pieces to fit short side of the flat bread; set aside.
In small skillet heat 2 teaspoons olive oil over medium heat. Add mushrooms and stir to evenly coat. Cook 2 minutes, stirring frequently until mushrooms release their moisture. Continue cooking 3 to 5 minutes, stirring occasionally, until liquid has evaporated and mushrooms become tender and start to darken.
With pastry brush spread 1 tablespoon horseradish sauce on each flatbread (bubble-side-down). Layer 1 flatbread with roast beef, mushrooms, additional horseradish sauce, provolone cheese, asparagus spears and onion. Top with remaining flatbread. Lightly brush sandwich top and bottom with olive oil.
Heat grill pan over medium heat; brush pan with remaining olive oil. Place sandwich in center of pan; top with skillet. Place 2 unopened food cans in center of skillet to weight the sandwich. Grill 1 to 2 minutes per side or until cheese is melted. Rotate sandwich half way through cooking time to make cross grill marks on the sandwich. Cut into quarters to serve.
- 8 medium fresh asparagus spears, washed and trimmed
- 3 tablespoons olive oil, divided
- 1/8 teaspoon coarse sea salt
- 4 medium mini bella mushrooms, thinly sliced
- 3 tablespoons horseradish sauce, divided
- 2 9x7-inch whole grain flatbread
- 5 ounces thinly sliced deli roast beef
- 4 ounces deli-style sliced smoked Wisconsin Provolone cheese
- 1/4 cup red onion, thinly sliced