Ok, so here we are.
Keep in mind that quantities are just an indication; you've got to find the exact amount of each one, to suit your taste. Some people i know don't even follow any fixed quantity, they just taste everything while making it, to assure that any component is present in the optimal ratio.
Take the zest of 4 lemons, and put it in jar with 0,5 lt of pure alcool (It doesn't need to be finely chopped, look at the picture above. You just have got to cut it like if you where peeling an apple. Maybe is even better because you get more lemon oil in the final product).
Leave the lemon zests there for 10-15 days, in a, fresh, dark spot of your house. Then filter the alcool taking away the zests: you can trow the zests away at this point.
Then take 1 lt of milk, and heat it almost to the boiling point, and mix it with 500gr of white sugar. Mix it till the point where the sugar is completly dissolved.
Wait for the milk to cool down at room temperature. Once it is cold you can add the cream. We go with 250 grams of cream, at 30% of fat. Your mileage may vary: i don't know how much fat is in your cream.
Anyway add the cream with the milk, mixing with a spoon, then add slowly the alcool to the milk, mixing with a spoon.
Let it sit for a month (in freezer) then drink.
Keep in mind that cream and alcool don't mix well, without additives; so you can occasionally find some cream grumes, expecially if you used too much cream.
If you can't stand them (like i do), you've got to reduce the amount of cream used in this recipe (you can even avoid adding cream completly). Remember anyway that you've got to shake the bottle every time before serving.
You've got to keep it in freezer because, unlinke limoncello, it goes bad at room temperature.
I hope to have explained it in a undestandable way.