I made a garlic mayonnaise the other day which worked really well (if a bit strong!!). 3 cloves of garlic (or more if you love garlic), 2 large egg yolks, 1 tsp dijon mustard, juice of 1/2 lemon, 200ml/7fl oz groundnut oil, salt and pepper. Crush the garlic in a pestle and mortar and whisk the eggs with the mustard, lemon and salt & pepper. Drip the oil in using an electric whisk to beat - I find that if you drop the oil over the whisks you don't get a big dollop of oil in at once. The reason mayo splits is because the oil needs to be added really slowly, esp. at the beginning (basically you need to coat each drop of oil with the egg mixture) - sounds like a nightmare performance which it can be but as you get more oil incorporated you can increase the speed you drop the oil in. You can replace the garlic with herbs or whatever else you like really - I'm just not sure how adding additional lemon juice would affect the balance of the mayo - maybe it would work if you added some grated lemon rid? Good luck!