Step 1In a small mixing bowl, macerate the shallots in the red wine vinegar until they soften slightly, about 5 minutes. Add the mayonnaise and blue cheese and stir roughly with a fork, mashing any large clumps of cheese with the tines of the fork. Stir in just enough heavy cream to make a slightly creamy consistency; the dressing will be very thick. Add salt to taste; because blue cheese can be quite salty, it might not need any. Stir in a generous grinding of black pepper and refrigerate tightly covered. Let warm slightly and stir briskly before serving.
Step 1In a large skillet, cook the bacon over medium-low heat until it is browned on 1 side, about 5 minutes. Turn and brown on the other side, 4 to 5 minutes. If there are any pale spots left on the first side, turn it again and cook briefly so that the bacon is well-browned and quite crisp. Drain on paper towels.
Step 2Pull away any tough or faded outer leaves from the romaine, then separate the heads into individual leaves and combine in a large mixing bowl.
Step 3Spoon over about one-half cup of the blue cheese dressing and toss, adding more dressing 1 tablespoon at a time as needed to lightly coat the leaves.
Step 4Arrange the romaine on 6 chilled salad plates, then crumble the bacon over top and scatter the sliced radishes over everything.
Step 5Serve immediately.