Meanwhile, in a large saucepan, bring the chicken stock to a simmer; season with salt. Whisk in the semolina in a thin stream and bring to a boil, whisking to prevent lumps. Cook, stirring, until thick and creamy, about 3 minutes. Stir in the butter and cheese and season with salt and pepper. Pour the semolina into a large bowl and top with the roasted mushrooms. Garnish with the parsley and serve.