1. In a bowl, cover pecans with at least 1 inch water and let soak for 1 hour.
2. Meanwhile, adjust oven rack to middle position and preheat oven to 260°C. Place cauliflower on a foil-lined rimmed baking sheet, toss with olive oil, and season with salt and pepper. Roast, flipping cauliflower with a thin metal spatula halfway through roasting, until tender and deeply browned on both sides, about 20 minutes total.
3. In a large saucepan, melt butter over medium-high heat. Add onion, garlic, and cayenne and cook, stirring often, until softened and just starting to turn golden, about 4 minutes. Add brandy and cook until completely evaporated.
4. Add cauliflower, cream, and thyme. Drain pecans and add to saucepan. Bring to a simmer, then cook, adjusting heat to maintain simmer, until cauliflower has softened and liquid has reduced to about 3/4 cup, about 10 minutes. Discard thyme sprig. Add soy sauce.
5. Using a blender or immersion blender, blend cauliflower and liquid to form a very smooth purée. Season with salt and pepper. To chill rapidly, spread vegetarian pâté in a thin, even layer on a parchment-lined baking sheet (a quarter-sheet size is best for this), then press plastic wrap directly against pâté's surface, pushing out any air. Otherwise, transfer pâté to a heatproof container and press plastic directly against surface. Refrigerate until well chilled. Transfer to a serving vessel and serve with crackers or toasted baguette rounds.

Notes - While the final texture and flavour won't be as luxuriously silky and rich, you can make this recipe vegan by using oil in place of the butter and vegetable stock in place of the cream.