Preheat the oven to 200 °C top/bottom heat and line a baking sheet with baking paper.

Peel the sweet potatoes and cut them into approx. 1.5 cm cubes. In a bowl, toss thoroughly with 15 ml olive oil, half of the plucked thyme leaves, and a little salt and pepper. Spread evenly on the baking sheet and roast in the oven for approx. 22–25 minutes until golden brown and tender.

Meanwhile, rinse the beluga lentils with cold water in a sieve. Bring to a boil in a small pot with plenty of salted water and cook over medium heat for approx. 20–25 minutes until al dente. Then drain through a sieve and allow the steam to evaporate briefly.