Heat a saucepan with a lid over medium to medium-high. Add the almonds and toast until light golden; transfer to a plate. Add the butter to the pan. When it foams, add the spaghetti and cook until browned, about 2 minutes. Add the rice, season with salt and pepper and stir to coat. Add 2 cups stock and bring to a boil. Reduce the heat to low, cover and simmer until the rice is tender, shaking the pan occasionally and adding more stock if the rice is too dry, 15 to 18 minutes. Stir in the almonds.
Meanwhile, season the chicken with salt and pepper. In a large skillet, heat the olive oil, two turns of the pan, over medium-high. Add the chicken and cook until browned, 3 to 4 minutes per side; transfer to a plate. Add the butter to the skillet. When it foams, add the spring onion whites, thyme and garlic; season. Swirl the skillet for a minute or two; whisk in the flour and then the wine. Simmer for a few seconds to reduce slightly, then whisk in the stock. Bring to a bubble, return the chicken to the skillet and simmer until the chicken is cooked through, 3 to 5 minutes. Transfer the chicken to plates and pile the rice alongside. Stir the spring onion greens and the lemon juice into the sauce. Spoon the sauce over the chicken and rice.