Preheat your oven to 350°F (175°C) and grease a 9×9-inch baking dish.
Heat vegetable oil in a large skillet over medium heat. Add sliced onions and jalapeños, and sauté until softened, about 3-4 minutes.
Add diced tomatoes and minced garlic to the skillet, stirring to combine. Cook until the vegetables are softened, about 3-5 minutes.
In a mixing bowl, whisk together the heavy cream, sour cream, cayenne pepper, chipotle chili powder, cumin, and a pinch of salt. Pour this mixture into the skillet with the vegetables and stir to combine. Bring the sauce to a gentle simmer over medium-low heat.
Add the shrimp to the pan, nestling them into the sauce. Cook the shrimp until they are opaque on one side, then flip and cook until fully opaque and cooked through. Remove the pan from the heat.
To assemble the enchiladas, divide half of the grated Monterey Jack cheese evenly among the four tortillas, spreading it down the center of each one.
Using a slotted spoon, scoop out about a quarter of the shrimp and veggie mixture, draining off excess sauce, and place it over the cheese in each tortilla. Roll up the tortillas and place them seam-side down in the prepared baking dish.
Pour the remaining sauce from the skillet over the enchiladas, making sure they are fully covered. Sprinkle the remaining grated cheese over the top.
Bake the enchiladas for 15-18 minutes, until the cheese is melted and bubbly. Serve hot, and enjoy!