Place a large saucepan with a lid over medium–high heat. Melt the butter and olive oil, then throw in the chicken pieces and brown on all sides – this will take roughly 5 minutes. Throw in the leek and garlic cloves and toss them with the chicken, then season with the salt. Cook for 2 minutes, until the leek starts to soften.Pour in the white wine and bring to a simmer, using a spoon to scrape all the sticky bits off the bottom of the pan. Simmer for 2 minutes, then pour in the chicken stock or water, followed by the potatoes, bay leaves and plenty of black pepper. Taste and adjust seasoning if needed. Bring back to a simmer, then reduce the heat to low, put the lid on and cook for 30 minutes, stirring every now and then. Check the potatoes are cooked by piercing them with a knife – they should be soft and offer no resistance. Turn off the heat then add the lemon juice, cream and baby spinach. Stir through to wilt the spinach. Fish out the garlic skins, and serve immediately with a good grind of pepper, an extra drizzle of cream, if you like, and fresh herbs.