Preheat your grill.
Take the leeks and clean well, between each layer. Massage with olive oil, salt and pepper and place on the grill to char, flipping occasionally. Remove and set aside to cool.
In the food processor, combine mayo, sour cream, lemon, olive oil, salt, pepper, garlic and smoked paprika.
Cut the leeks into 1-2 inch pieces and add to the food processor. Blend until combined. Splash a bit of warm water if needed to make a desired sauce consistency.
Adjust seasoning to taste, and scoop into a serving container. Set aside.
Using the already preheated grill, add the chicken thighs, skin side down, to get a crispy outer layer. Continue to flip until cooked thoroughly.
Clean and slice brussel sprouts and toss with olive oil, salt and pepper. Using your grill basket, cook these alongside the chicken.
When all is done, serve with a dollop of the charred leek sauce on top. Enjoy!