**Preheat the Oven**: Preheat your oven to 350°F (175°C). Grease a loaf pan or terrine mold with cooking spray or butter and line it with parchment paper for easy removal.
**Sauté the Leeks**: In a skillet, heat the olive oil over medium heat. Add the chopped leeks and sauté for about 5-7 minutes until they are soft and translucent. Remove from heat and let cool.
**Mix the Ingredients**: In a large mixing bowl, combine the ground chicken, sautéed leeks, chopped apricots, heavy cream, eggs, thyme, salt, pepper, and nutmeg. Mix until well combined but do not overmix.
**Transfer to the Pan**: Pour the chicken mixture into the prepared loaf pan, pressing it down gently to eliminate any air pockets. Smooth the top with a spatula.
**Bake**: Place the loaf pan in a larger baking dish filled with hot water (creating a water bath) to help cook the terrine evenly. Bake for about 1 hour, or until the internal temperature reaches 165°F (75°C) and the terrine is firm to the touch.
**Cool and Chill**: Once cooked, remove the terrine from the oven and let it cool in the pan for about 10 minutes. Then, carefully remove it from the pan and refrigerate for at least 4 hours, or overnight, to allow it to set.
**Serve**: When ready to serve, slice the terrine into thick pieces. Garnish with fresh parsley and serve with crusty bread, crackers, or a light salad.