Cut the chicken fillet into strips, chop the mushrooms, cut the leeks into rings, separate the romanesco into florets, and dice the onion.
Bring a pot of water to a boil and blanch the romanesco florets for 3-5 minutes until tender and bright green. Drain and set aside.
Heat a large pan over medium-high heat. Add the diced onion and chicken strips and fry for 5-7 minutes until the chicken is cooked through (internal temperature 74°C/165°F) and the onion is softened. Add the chopped mushrooms and tomato paste, stir, and cook for 2 minutes. Season with salt, pepper, and sweet paprika powder.
Add the vegetable stock and leek rings to the pan. Simmer over medium heat for 10-12 minutes until the leek is tender and reduced in volume. Add the cream cheese and stir until smooth. Season with salt, pepper, and hot paprika powder to taste. Add the flour and stir well. Simmer for 2-3 minutes. Remove from heat and gently stir in the blanched romanesco florets.