Gourmet salad with Potatoes and Creameuse Vinaigrette

For vinaigrette:
1/2 cup mayonnaise
2 tbsp mustard
2 tbsp white vinegar
1/2 to 3/4 cup of olive oil (depending on the desired consistency)
1 clove of grated garlic
2 tbsp. chopped fresh parsley
Salt and black pepper to taste
For the salad:
5 medium-sized potatoes (smells and cut into medium slices)
3 hard-boiled eggs (cut into quarters or thin slices)
1 large fresh tomato (cut into pieces)
A little red onion (finely sliced)
1 lawyer (optional) (drawn for an additional creamy key)