Combine tomatoes and sliced mushrooms in a pan, season with cracked pepper and dry roast for about 15 minutes, or until the tomatoes have burst open and softened.
Meanwhile, fill a deep saucepan halfway with water and bring to a rapid boil. Crack an egg into the water and with a spoon whirlpool the water around the egg to create an even oval shape. Cook until the whites become firm and the yolk is still soft to the touch, 2 to 3 minutes.
Meanwhile, toast the muffins until lightly golden, then place on a plate.
Lift each egg from the water with a slotted spoon, allowing any excess water to drain back into the pan. Top the muffins with the roasted vegetables and poached egg, season with cracked pepper to serve.