For the topping:
1. Preheat the oven to 350(f) degrees. Line a baking sheet with foil.
2. Place potatoes cut side down on the prepared baking sheet & poke the skins with a fork. Roast until tender, about 50 minutes.
3. Once cool enough to handle, peel back the skins & transfer the flesh to a large mixing bowl. Add the garlic, sage, butter, heavy cream, salt & pepper.
4. Using electric hand beaters beat the mixture until fluffy & smooth. Set aside until ready to assemble.
For the filling:
1. In a large skillet over medium heat add the olive oil & ground beef. Break up the beef as it cooks & continue cooking until browned. Using a slotted spoon, transfer the beef to a bowl.
2. Drain excess liquid from the skillet before adding the garlic, shallots & sage. Cook until fragrant, about 2 minutes.
3. Add the beef back to the pot, followed by the vegetables. Cook until softened, about 5 minutes.
4. In a small measuring cup whisk together the stout, stock & flour to form a “slurry”. Pour the slurry over the beef filling & bring to a gentle simmer. Once the sauce has thickened slightly, remove from heat.
1. Preheat the oven to 400(f) degrees. Add the beef filling to a large baking dish (9 by 12-inch or 10-inch round) followed by the sweet potato topping. Use the back of a spoon to create swirls in the potatoes. Sprinkle the top with salt & pepper.
2. Bake until the edges begin to bubble, about 45 minutes. Set aside for 10 minutes before serving.