Add the onion and garlic to the bacon drippings and cook, stirring occasionally, until softened. Add the jalapeno and cook, stirring, until softened, about 1 minute. Stir in the roasted corn and heat thoroughly.
In a large bowl, whisk together the eggs, melted butter, masa, and cornstarch. Drizzle in the warm milk mixture, whisking constantly. Stir in the corn mixture until well blended. Stir in the thyme, sugar, and reserved bacon. Season with salt and pepper to taste.
Pour the mixture into the prepared 12-inch skillet and bake until the center is still jiggly but set, about 25 minutes.