1. Wash and gut the mackerel, then pat them dry with paper towels.
2. Make incisions on the belly side of the mackerel and flatten them slightly with the palm of your hand.
3. In a plate, mix the salt with the pepper and powdered thyme.
4. Roll the mackerel in this mixture and lightly coat them with olive oil using a brush.
5. Grill them in a pan on both sides.
6. Then prepare the sauce:
7. Meanwhile, peel and chop the shallots, then melt them with butter in a saucepan along with the lemon juice.
8. Then add the cream while stirring constantly and let it thicken over low heat.
9. Once the sauce has thickened, place the grilled mackerel on a hot serving dish, then coat them with the shallot cream.