Preheat oven to 200°C and place mushrooms on a rack on top of a baking tray.Brush with the olive oil and season to taste. Roast for 10-15 minutes until tender. In a large heavy based frying pan (or large cast iron pan) add a drizzle of olive oil. Sauté the onion and celery until tender. Add the tomato paste, harissa, garlic and cumin.Sauté until fragrant. Season. Add the tinned tomatoes and bring to a simmer. Simmer gently until the sauce has thickened slightly, about 10 minutes.Turn the heat off for a moment and make 4small wells in the sauce. Crack an egg into each well. Cover the pan with a lid and switch the heat back on to low. Cook the eggs for 8 to 10 minutes or until done to your liking. When the eggs are almost cooked nestle the portabello mushrooms into the sauce to reheat. Finish with a generous scattering of fresh coriander and serve with crusty bread.