Preheat the oven to 375°F (190°C).
In a large soup pot or wide Dutch oven (for one-pot cooking), heat the olive oil over medium heat.
Mince the onion, add to the heated pot. Stir once. Chop the leeks into thin strips, add them to the cooking onions and stir. Thinly slice both stalks of celery, and add to the pot, and stir. Slice both carrots in half, then chop into thin half-rounds, add to the pot and stir. Continue sautéing all the vegetables until the carrots begin to soft at the edges, about 5 minutes.
Meanwhile, drain the water off the soaked cashews. Place the cashews in a high-speed blender and add 1 -1 ½ cups vegetable stock (if using vegetable bouillon, add 3 teaspoons/cubes now plus 1 - 1 ½ cups water). Blend until the cashews and water become a smooth cream.
To the sautéing vegetables, add the thyme and chickpeas, stir, and continue cooking another minute.
Sprinkle the spelt flour over the sautéing vegetables and stir to fully distribute. Continue cooking until the raw flour disappears.
At this point, add the sherry if using and stir to deglaze the pan until the liquid mostly evaporates. Pour cashew cream into the pot. Pour the remaining 1 ½ - 2 cups vegetable stock (or water, if you’re using a bouillointo the blender and blitz for a few seconds to extract any last bits of cashew cream, then add to the pot. Stir and bring to a boil.
Reduce the heat to a low and simmer, stirring frequently, for 5 minutes, until the stew begins to thicken. Add the frozen peas, salt, and pepper, and stir to distribute.
Pour the stew into a 13-by- 9 inch baking dish (or keep in the Dutch oven). Place the pan/pot into the heated oven and cook for 15 minutes.
Meanwhile, prepare the biscuit dough. In a medium bowl, add the spelt flour, baking powder, garlic powder, pepper, and salt, then whisk to combine. In a small bowl or measuring cup, whisk together the milk, olive oil, and maple syrup. Pour the wet ingredients into the dry, stirring with a flexible spatula until just combined. Set aside to rest as the stew continues cooking.
After the stew has been in the oven for 15 minutes, remove it, and use a scantly-filled ¼ cup measure to drop the biscuit dough into 6 separated heaps on top of the stew. Sprinkle some extra freshly ground black pepper on top of the biscuits, then return the stew to the oven.
Continue cooking for another 20 minutes, until the stew is bubbling and the biscuits are slightly puffy and golden brown on top.
Serve hot, with a biscuit on top of each serving.