Bring 3 cups of the vegetable broth to a boil in a saucepan. Slowly stir in the grits. Return to a boil and cook for 3 to 4 minutes. Turn down the heat and stir in the Monterey Jack, Cheddar and cream cheese. Cook for another 3 to 4 minutes. Stir in 2 tablespoons of the butter and keep warm.
Heat the remaining 2 cups broth in a separate saucepan until hot.
Meanwhile, heat the oil and remaining 2 tablespoons butter in a large skillet over medium-high heat. Add the mushrooms, zucchini, corn, onion, bell pepper and jalapeno to the skillet and cook for 1 minute. Season the vegetables with the Cajun seasoning. Continue to cook until well browned, an additional minute. Add the tomato paste. Stir in the hot broth and add hot sauce and black pepper to taste. Cook until the vegetables are tender but not mushy, another 2 minutes. Add the lemon juice. Taste and adjust the seasoning.
To serve, spoon a hefty serving of grits into a bowl. Top with the veggies and sauce. Garnish with some scallions and serve.