Pat the chicken fillets dry and hammer flat to an even thickness.
Season both sides with black pepper, salt, lemon juice, and garlic powder, rubbing it in well.
Sear the chicken in a hot skillet for 5-6 minutes per side until golden and cooked to 165°F internally. Rest for 5 minutes, then slice.
In the same skillet, melt the butter and cook the minced garlic for 30 seconds until fragrant.
Add the mushrooms and sauté for about a minute.
Lower the heat, stir in the cream, then add the milk and mix until combined.
Add the chicken stock cube, salt, dried oregano, and garlic powder, stirring well.
Add the grated and sliced cheddar, stirring constantly over low heat until melted and smooth.
Add the fettuccine (boiled as per pack's instructions) and toss to coat.
Plate the pasta, top with sliced chicken, and garnish with basil leaves.