Get out a baking dish that measures 9 by 13 inches and spread some grease over the bottom and sides of it.
In a large mixing bowl, combine the cottage cheese, butter, and eggs. Use a whisk or an electric mixer to beat these ingredients together until they are smooth and creamy.
Add the cornbread mixes to the bowl, stirring gently until the mixture is just moistened. Don't over-mix, as this can make the cornbread tough.
Add the chopped broccoli, onion, and one cup of the Cheddar cheese to the bowl. Use a spatula to fold these ingredients into the batter, being careful not to over-stir.
Pour the batter into the prepared baking dish, spreading it evenly. Sprinkle the remaining half-cup of Cheddar cheese over the top of the batter.
Place the baking dish in the preheated oven and bake for 35 to 40 minutes. To check if the cornbread is done, insert a toothpick into the center of the dish. If it comes out clean, the cornbread is ready.
When the cornbread is finished baking, take it out of the oven and let it cool in the dish for 10 minutes before slicing and serving. The cornbread will be easier to cut if you let it cool slightly before serving.