These are lovely, easy and healthy and are also great to take on picnics. The jars are gorgeous and I found them on a website called;
http://weckjars.com/
They are a German brand, stocking all sorts of shapes and are so attractive looking.
You can make these in advance up to 3 days, cover them and refrigerate. Take them out about 30 mins before serving to allow them to come up to room temperature.
There are several stages to this dish, hence the pretty layers, but they are simple.

**There is one step in this preparation that can make it even more simple. 
In Los Angeles we can buy pre-cooked vacuum packed puy lentils in our supermarkets that are already  seasoned. 
Instead of making them from scratch, you can buy 1 packet of these, (you need 2 &1/4 cups of the cooked ones) put them into a microwaveable dish, break them up a bit gently with a fork and reheat.  Let come to room temp, fluffing up the lentils to break up the lumps, then proceed with adding the goat cheese and cream etc… 

8 1/4 cups water
8 oz carrots (about 3 medium) peeled and diced small
1 1/2 tsp kosher salt, plus more if needed
Freshly ground black pepper
1 cup plus 2 tbsp heavy cream
1 large egg
1 tbsp olive oil
1lb plus 10 oz leeks (about 2 -3 medium) quartered lengthwise and thinly sliced crosswise (white and light green parts only)
1 tsp finely chopped fresh thyme leaves
10 oz zucchini (about 2 medium) trimmed and diced small
1 cup French Puy lentils, rinsed
1 bay leaf
1 medium garlic clove, smashed and peeled
4 oz fresh goat cheese, at room temp

Heat the oven to 325 F and arrange a rack in the middle.  Bring 8 cups of the water to a simmer in a large saucepan over high heat; keep at a simmer.

Meanwhile, bring the remaining 1/4 cup of water to a simmer in a large frying pan over medium heat. Add the carrots and 1/2 tsp of the salt and season with pepper. Reduce the heat to medium low, cover with a tight fitting lid and cook until softened, about 5 minutes. Using a slotted spoon, transfer 1/2 cup of the carrots to a small bowl and transfer the remaining carrots to a blender, leaving any excess water in the pan; set both aside. Reserve the carrot juices in a small bowl, wipe out the frying pan and set aside.

Place 1 cup of the cream and the egg in the blender with the carrots, season and blend until smooth, about 30 seconds. Evenly divide the carrot-cream mixture among 6 (1/2 pint) tempered-glass jars. Divide the reserved 1/2 cup carrots among the jars. Evenly space the jars in a 13 x 9 inch glass baking dish.
Being careful not to get water inside the jars, add enough of the simmering water to the baking dish so that it reaches just past the carrot mixture in the jars.
Cover the baking dish tightly with aluminum foil and carefully transfer it to the oven.
bake until the outer 1 inch of each carrot custard is set (the centers will be still slightly jiggly), about 25 minutes.

Heat the olive oil in the reserved frying pan over medium heat until shimmering. Add the leeks and thyme, season with salt and pepper and cook, stirring occasionally, until just starting to soften, about 6 minutes.
Add the zucchini, season with salt and pepper and stir to combine. Cook, stirring occasionally, until the zucchini is crisp-tender and the leeks are completely softened, about 4 minutes more.
Remove the pan from the heat and set aside.

Place the lentils, bay leaf and garlic in a medium saucepan and cover with cold water by 2 inches.
Bring to a boil over high heat. Reduce the heat to medium low and simmer, stirring occasionally, until the lentils are still slightly hard in the center, about 10 minutes.
Add the remaining teaspoon of the measured salt, stir to combine and continue to simmer until the lentils are just tender, about 3 to 4 minutes more.
Drain though a large fine-mesh strainer.
Remove the garlic clove and bay leaf and transfer the lentils to a medium bowl.
Add the goat cheese and the remaining 2 tbsp cream, adjust seasonings if necessary and stir to evenly combine; set aside.

When the carrot custards are ready, carefully remove the jars from the hot water and transfer to a wire rack to cool slightly, about 15 minutes.

To assemble the terrines, divide all of the lentil-goat cheese mixture over the carrot custards, using your fingertips to gently smooth it into an even layer.
Divide all of the leek-zucchini mixture over the lentil-goat cheese mixture.
Serve warm or at rom temperature, or let the terrines cool completely, cover tightly and refrigerate for up to 3 days