Bring a large pan of water to the boil. Heat 2 tbsp oil in a large saucepan. Add the diced shallot and cook for 5 minutes. Add the flour and stir until a paste forms, then cook for a further 2 minutes. Gradually add the almond milk and stir until smooth, then add the garlic powder, nutmeg and some seasoning and simmer over a medium heat until thickened.
Heat the remaining 1 tbsp olive oil in a wide pan over a high heat and add the mushrooms. Cook for 6-7 minutes until golden brown and softened. Add the crushed garlic and thyme and cook for a further 2 minutes, then add this to the almond milk sauce and season to taste. Remove the sauce from the heat and cover to keep it warm.
Meanwhile, cook the spaghetti according to the instructions on the packet. Scoop out two ladlefuls of cooking water then drain the rest. Stir the pasta through the mushroom sauce with the parsley and add some of the cooking water to loosen it. Divide between 4 plates and top with the toasted almonds to serve.