Heat olive oil over a medium skillet over medium-high heat and sauté brussels sprouts and leeks until softened. Season with salt and pepper. Place in a bowl and set aside.
In the same skillet, brown chicken cubes and add 2 tablespoons of the sriracha bbq sauce to the skillet to coat the chicken. Remove from heat and set aside.
On a large baking sheet, arrange tortillas.
Evenly divide the remaining sriracha bbq sauce amongst the tortillas and spread a thin layer onto each tortilla (like the tomato sauce for pizza).
Evenly divide the brussels and leek mixture on top of the sauce then evenly divide the cubed chicken.
Sprinkle mozzarella on top and bake in the oven for 7-10 minutes, or until cheese has melted and ingredients have warmed through.
Drizzle additional sriracha bbq sauce on top, if desired.
Notes
I used Trader Joe's sriracha bbq sauce but you can make your own! Just add as much sriracha as you want to your bbq sauce ;) I know it sounds silly but that's really all there is to it! Maybe some minced garlic too, if you like!