Mix the yoghurt with the Feta cheese, smashing the cheese with a fork to combine well into a chunky sauce. Cut the garlic clove in half lengthwise and add to the yoghurt mixture. Set aside.
Heat a large sauté pan over a medium heat and add the butter and oil. Once the butter starts to foam add the leeks and spring onion, season with sea salt and black pepper. Fry the vegetables for 2 minutes, stirring until the leeks are soft. Add the cumin seeds and vegetable stock and boil the mixture until the stock has evaporated. Add the peas and spinach and cook for 1 minute until the spinach has wilted, then reduce the heat to a low to medium heat.
Make a well in the leek and pea mixture and break an egg into the space. Repeat with remaining eggs, then season each yolk with salt. Cook the eggs for about 4-5 minutes over a low heat, or until the egg whites are cooked and the yolks are runny.
Remove the garlic halves from the yoghurt and Feta sauce and serve with the baked eggs. Serve with a wedge of lemon.