Put the oyster leaves, parsley, vegetable oil, garlic and shallot in a blender and blend for about 8 minutes or until the oil reaches 75C (167F). Strain and let cool. Put the egg yolks, mustard and vinegar into the clean blender and blend. With the blender running, add the green oyster leaf oil and continue blending until the mixture is completely emulsified. Season to taste with salt and lemon juice.