Prepare all ingredients. Preheat the oven to thermostat 8.
Stick the cloves in the roast and place in a baking dish.
Pour the vegetable stock on the roast. Add salt and pepper.
Place in the oven and bake for 20 minutes.
Meanwhile, remove the green parts of the leeks, wash them and slice them.
Peel the carrots and slice them.
Peel the celery and slice it in small pieces.
Peel and thinly the onion.
Place a knob of butter in the bottom of a pan and brown all the vegetables along with the chopped garlic for 3 to 4 minutes. Lightly salt and pepper.
Remove from the oven after 20 minutes,...
...flip over, baste with its sauce...
...and place the vegetables all around.
Sprinkle with a little bit of lemon juice and bake for another hour.