Preheat the oven to 375 degrees Fahrenheit and set aside two large ramekins.
Heat the olive oil in a skillet over a medium/high heat. Add the diced pancetta and cook through until crisp and golden. Remove from the skillet using a slotted spoon and set to one side.
Roughly dice the tomatoes and finely chop the onion. Add to the skillet that was used to cook the pancetta and sweat over a low/medium heat until tender and fragrant.
Add the baby spinach to the skillet and stir well to combine, cooking gently until the leaves are just wilted.
Remove the skillet from the heat and return the diced pancetta along with the parmesan and a pinch of salt and pepper. Stir everything together until well combined.
Divide the spinach and pancetta mixture evenly between the two ramekins, creating a well in the center of each. Crack an egg carefully into the center of each well. Arrange the ramekins on a shallow oven tray and transfer to the oven to bake for 10-12 minutes or until the eggs are cooked through. Scatter with chopped fresh basil to serve.