Remove the Porterhouse steak from the refrigerator and let it sit at room temperature for about 30-45 minutes. Season generously with salt and black pepper on both sides.

In a bowl, combine the sliced shallots and all-purpose flour. Toss until the shallots are evenly coated.

In a large skillet, heat the vegetable oil over medium-high heat. Once hot, add the coated shallots in batches, frying until golden brown and crispy, about 3-5 minutes. Remove with a slotted spoon and drain on paper towels. Season with a pinch of salt.

Preheat your oven to 400°F (200°C). In a large oven-safe skillet, heat a tablespoon of oil over high heat. Add the Porterhouse steak and sear for about 4-5 minutes on each side until a crust forms.

Transfer the skillet to the preheated oven and roast for about 10-15 minutes for medium-rare, or until your desired doneness is reached. Use a meat thermometer for accuracy (130°F for medium-rare).

In a small saucepan, melt the unsalted butter over medium heat. Continue cooking until it turns golden brown and has a nutty aroma, about 5-7 minutes. Carefully add the dry sherry and bring to a simmer, scraping up any browned bits from the bottom of the pan.

Stir in the fresh thyme leaves and the fried shallots. Cook for an additional 2-3 minutes to heat through.

Remove the steak from the oven and allow it to rest for about 5-10 minutes before slicing. Plate the steak and drizzle the brown butter and sherry-shallot infusion over the top. Garnish with chopped parsley and additional fried shallots.

Slice the steak and serve immediately, enjoying the crispy shallots and rich flavors of the infusion.