1. Cut the tomatoes into quarters and set aside.
2. In a small bowl, whisk the mustard with the vinegar. Slowly add the oil while whisking. Season with salt and pepper. Set aside.
3. In a pan, melt the butter. Break in the eggs and cook without turning.
4. Meanwhile, place the crepes flat on plates.
5. Top each crepe with rocket and a fried egg.
6. Divide the tomatoes among the 4 plates and drizzle with the vinaigrette. Serve immediately.