Pour brandy over nectarines and soak for about 30 minutes.
For the lemon cream: Pour the milk and heavy cream into a heavy bottomed saucepot and add vanilla and lemon liqueur. Add half the sugar to the pot and bring to a simmer (just below a boil). In a small bowl whisk together the egg yolks and the rest of the sugar and temper it by adding a small amount of the heated milk mixture to the bowl while whisking constantly (known as a liaison). Now pour the liaison (egg mixture) into the milk pot, stirring constantly. You are only heating it. Do not boil. Do not cook. The idea of a liaison is to incorporate the eggs and avoid making them into scrambled eggs! You want the mixture to begin to thicken so it will coat the back of a spoon. Remove from heat and whisk in lemon zest, and allow to cool, then remove vanilla pod and discard, and refrigerate until chilled.
Place nectarines cut side up in a pan and sprinkle with 1 tablespoon sugar. Spoon brandy around nectarines, cover and heat nectarines and brandy briefly. Then remove cover and spoon warmed brandy over nectarines. * Remove from the heat and ignite with a long match to flambe. Alternatively, you can grill the brandy soaked nectarines until they begin to caramelize. Allow nectarines to cool to room temperature.
Place 2 nectarines on each serving dish, and top with lemon cream and blackberries.