For crepe batter, in a blender or food processor combine milk, flour, masa harina, eggs, and the 1/4 teaspoon salt. Cover and blend or process until smooth, scraping side as needed. With motor running, add melted butter in a steady stream through the opening in the lid, blending or processing until incorporated. Let stand for 30 minutes.
Meanwhile, preheat oven to 425 degrees F. Line a baking sheet with foil. Cut chile pepper in half lengthwise; remove seeds and membranes. Place pepper halves, cut sides down, on prepared baking sheet. Roast for 20 to 25 minutes or until skin is blistered and dark. Bring the foil up around pepper to enclose. Let stand for 20 to 30 minutes or until cool enough to handle. Using a paring knife, loosen edges of the skin from the pepper; gently and slowly pull off the skin and discard. Chop pepper.
For sauce, in a small saucepan combine whipping cream and chopped chile pepper. Bring just to boiling; reduce heat. Simmer, uncovered, about 5 minutes or just until thickened. Add the 1/4 cup cheese, stirring until melted. Cool slightly. Transfer batter to a food processor or blender. Cover and process or blend until smooth. Season to taste with additional salt.
Heat a lightly greased 6-inch skillet over medium to medium-high heat; remove from heat. Spoon 3 tablespoons of the crepe batter into skillet; lift and tilt skillet to spread batter. Return to heat. Brown crepe on one side about 1 minute; turn and brown briefly on the other side. Invert the crepe onto a paper towel. Repeat with the remaining batter, greasing skillet occasionally.
In a large skillet heat oil over medium heat. Add carrot and onion; cook about 4 minutes or until softened. Add zucchini and summer squash; cook about 4 minutes more or until tender. Season to taste with salt and black pepper.
Fill crepes with vegetable mixture and roll up. Reheat sauce, if desired, and drizzle over crepes. Sprinkle with additional cheese, if desired.