Place the eggs, milk, 1/4 teaspoon salt, melted butter, and flour into a blender. Blend until no dry lumps of flour remain in the batter. Scrape down the sides of the blender as needed. Heat an oiled, non-stick skillet over medium heat. Pour in enough batter to cover half of the skillet. Tip and rotate the skillet until the batter covers the entire area. Cook until the batter turns from wet to moist, and the edges begin to curl away from the sides of the skillet. Turn the crepe over, and continue cooking until lightly golden on the other side. Place the crepe onto a plate, and cover with a kitchen towel to keep moist. Repeat with the remaining batter, lightly oiling the skillet as needed to keep the crepes from sticking.
Melt 2 tablespoons of butter in a large pot over medium heat. Stir in the garlic and onion, and cook until the onion has softened and turned translucent, about 5 minutes. Pour in the chicken broth, and simmer until reduced to half its original volume. Stir in the chopped zucchini blossoms, cover, and cook a few minutes until the squash blossoms have softened and reduced in volume. Stir in the tomato, nutmeg, and epazote until the tomato begins to soften, about 2 minutes. Add the creme fraiche, then season to taste with salt and pepper.
Roll about 2 tablespoons of zucchini filling in each crepe, and place into a 9x13-inch baking dish. Pour the half-and-half cream evenly over top of the crepes, and sprinkle with grated Manchego cheese. Cover the dish with aluminum foil, tenting if necessary so the foil does not touch the cheese.
Bake in the preheated oven until the crepes are hot and the cheese has melted, about 10 minutes.