1 small head of cauliflower, sliced into 3/8" thick steaks
1 tablespoon olive oil
Salt, to taste
Freshly ground black pepper, to taste
1/4 cup mayonnaise
1 garlic clove, minced
2 teaspoons whole grain mustard
2 teaspoons fresh lemon juice
2 tablespoons butter, softened
4 slices pumpernickel bread
4 slices Havarti cheese
4 fresh basil leaves
Preheat oven to 400 degree Fahrenheit. Brush cauliflower steaks with olive oil and then season with salt and pepper. Place the cauliflower into the oven and roast for 20 minutes, until cauliflower is tender and starting to brown. Remove from oven and allow to cool slightly.
In a small bowl combine mayonnaise, garlic, whole grain mustard, and lemon juice. Season lightly with salt and pepper.
Butter each slice of bread on one side and lightly spread the aioli on the other side. Lay two slices of bread, butter-side down, in a skillet and top with two slices of Havarti cheese, one cauliflower steak (or two, if they're small), and four fresh basil leaves. Top each sandwich with two remaining slices of bread, butter-side up.
Fry the sandwiches over medium heat, until the bread is toasted on one side and the cheese has started to melt, about five minutes. Gently flip and fry for about 3 minutes on the other side, until that bread has also started to toast. Remove from heat and wait five minutes before slicing and serving.