1. Combine the heavy cream, mustard, salt, and pepper in a large bowl, mix well until smooth, the mixture should be free of lumps.

2. Add the chopped red onion, parsley, and dill to the bowl and stir until they are evenly distributed throughout the dressing, ensuring all ingredients are well incorporated.

3. Gently fold in the cooked and sliced potatoes, approximately 250 grams or 8.8 ounces, until they are well coated with the dressing, be careful not to break the potatoes.

4. Cover the bowl with plastic wrap and refrigerate at a temperature of 4 degrees Celsius or 39 degrees Fahrenheit for at least 30 minutes to allow the flavors to meld together, this step is crucial for the development of the flavors.

5. Serve the potato salad chilled, at a temperature of around 4 degrees Celsius or 39 degrees Fahrenheit, garnished with additional chopped fresh herbs if desired, such as parsley or dill, which will add a burst of freshness to the dish.