How to Make It
Preheat the oven to 425°. Bake the potatoes directly on the upper rack of the oven for 40 minutes, or until tender.
Meanwhile, spread the fennel wedges in a shallow glass baking dish and drizzle with the wine and olive oil. Season with salt and pepper. Cover the dish with foil and bake in the bottom third of the oven for 40 minutes, or until the fennel is tender and golden brown on the bottom. Let cool slightly, then chop enough of the roasted fennel to measure 3/4 cup.
Cut one-quarter of the cheese into 8 slices. Cut the remaining cheese into small dice and transfer to a medium glass bowl. Add the milk and cook in a microwave at high power for 1 minute, or until the milk is very hot and the cheese is softened.
Halve the warm baked potatoes lengthwise. With a spoon and working over a bowl, scoop out the potatoes to within 1/4 inch of the skins. Using a masher or a large fork, coarsely mash the potatoes with the butter. Pour in the hot milk, stopping before you reach the cheese at the bottom of the bowl. Add the garlic and mash the potatoes until smooth and fluffy. Stir in the softened cheese and the chopped roasted fennel. Season with salt and pepper. Spoon the stuffing into the potato skins and transfer to a baking sheet. Top each potato half with a slice of the remaining cheese.
Bake the potatoes in the upper third of the oven for 12 minutes, or until they are hot throughout and the cheese is melted. Sprinkle the chopped fennel fronds over the potatoes and serve with the roasted fennel wedges.