2 egg yolks, cold
1 tablespoon Dijon mustard
½ cup olive oil
½ cup vegetable oil
2 tablespoons fresh dill, chopped
1 cup buttermilk, cold
1 ½ tablespoons red wine vinegar
Salt and freshly ground black pepper, to taste
In a large bowl, add the egg yolks and mustard and whisk until just combined (you can also use an electric mixer or food processor).
Continue to whisk while slowly drizzling in the olive oil and vegetable oil. Start very slowly and gently increase the flow so as not to break the emulsion.
When the mixture is thick and creamy, add the dill. Stir in the buttermilk, red wine vinegar, salt, and pepper and taste for seasoning.