- 1 egg yolk, at room temperature
 - 3 1/2 tablespoons sunflower oil, or as needed, divided
 - 1 tablespoon Dijon mustard
 - salt and ground black pepper to taste
 - 2 ripe avocados, sliced
 - 12 ounces precooked prawns, peeled and deveined
 
- Combine egg yolk, 1 teaspoon sunflower oil, and Dijon mustard in a bowl; whisk until smooth. Pour in remaining oil gradually, continuing to whisk, until sauce is smooth. Season with salt and pepper.
 - Arrange avocado slices in the center of a serving platter. Scatter prawns around the avocados. Pour sauce over avocado.