01 - Preheat oven to 400°F. Slice the top off the garlic head to expose the cloves. Drizzle with olive oil and a pinch of salt, then wrap tightly in aluminum foil. Roast for 30 to 35 minutes until cloves are soft and deeply golden. Let cool, then squeeze the roasted cloves from their skins and mash into a smooth paste.
02 - Heat neutral oil in a small saucepan over medium heat. Add sliced shallots in small batches and fry, stirring frequently, until golden brown and crisp, 3 to 5 minutes per batch. Transfer with a slotted spoon to paper towels to drain, then sprinkle lightly with salt. Set aside.
03 - Bring a large pot of generously salted water to a rolling boil. Cook radiatori according to package directions until al dente. Reserve 1 cup of starchy pasta water before draining.
04 - In a large skillet, melt the butter over medium heat. Continue cooking, swirling the pan occasionally, until the butter foams, turns a deep golden brown, and releases a nutty aroma, about 3 to 4 minutes. Watch carefully to prevent burning.
05 - Reduce heat to low. Add the miso paste and mashed roasted garlic to the brown butter, whisking vigorously until fully emulsified and smooth.
06 - Add the drained pasta to the skillet and toss to coat evenly. Stir in the Parmesan cheese and a splash of reserved pasta water, mixing until a glossy, silky sauce forms. Add lemon juice if using. Season generously with black pepper and adjust consistency with additional pasta water as needed.
07 - Divide the pasta among warmed plates. Finish each portion with a generous scattering of crispy shallots, an extra shower of Parmesan, and a sprinkle of fresh herbs if desired. Serve immediately.