Step 1 Cook the bacon strips over medium heat until the fat is rendered and the strips are crisp, about 10 minutes. Drain the bacon on paper towels, reserving 3 tablespoons bacon grease.
Step 2 Remove any wilted outer leaves from the radicchio and slice it lengthwise into eight wedges. Trim the top off the fennel, halve it lengthwise, then slice it crosswise into half-inch strips, discarding the core. Core the apples and cut each into 8 wedges.
Step 3Whisk together the shallots, thyme, rosemary, maple syrup, vinegar, bacon grease and olive oil. Season with one-half teaspoon salt and a grind of black pepper, or to taste. This makes about 1 cup vinaigrette.
Step 4Brush the apple wedges with a little of the vinaigrette and place them on an oiled grill heated over medium-high heat. Grill the wedges for about 2 minutes on each side, until slightly softened with defined grill marks. Remove and reserve in a warm place. Do the same with the fennel and radicchio.
Step 5Divide the apple, fennel and radicchio among 4 plates. Crumble the blue cheese over the salads, and sprinkle over the bacon. Drizzle 1 to 2 teaspoons of the remaining vinaigrette over each salad. Serve immediately.