Charred Corn Risotto with Crispy Portobellos and Tarragon

Name: Charred Corn Risotto with Crispy Portobellos and Tarragon
Ingredients: ¼ cups vegetable oil, plus more as needed; 2 portobello mushrooms, stems/gills removed, cleaned and sliced thinly; 6 - 8 cups water; 4 ears, sweet corn, shucked; 6 tablespoons unsalted butter, divided; 2 medium-sized shallots, minced; kosher salt; 2 cloves of garlic, minced or grated; red chile flake; 2 cups risotto rice (Carnaroli, Arborio or Vialone Nano); ½ cups dry white wine; ½ cups freshly grated Parmigiano-Reggiano, plus more for service; ½ cups coarsely chopped, fresh tarragon, plus more for service