Put the bacon in a small skillet over medium heat and cook, stirring occasionally, until crisp about 8 minutes. Transfer the bacon to a paper towel-lined plate and reserve the bacon drippings in the skillet.
Whisk the mayonnaise, sour cream, vinegar, 1 teaspoon of reserved bacon drippings and a pinch of salt and pepper together in a small bowl.
Brush the cut sides of the lettuce with additional bacon drippings and season with a pinch of salt and pepper. Lightly oil the grill grates. Grill the lettuce, without flipping, until lightly charred and wilted, about 2 minutes. Transfer to a serving platter. Pour the dressing over the lettuce and scatter the crisp bacon and blue cheese on top.
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