Prepare Jiffy Mix corn muffins according to the package instructions. Cool the cornbread completely before making the casserole.

Preheat oven to 350 degrees.

Place zucchini and yellow squash in a large saucepan and add just enough water to cover.

Cook on medium-low heat just until tender.

Remove the squash from the heat.

Drain squash, reserving one cup of the cooking water for the casserole.

Melt the butter in a large saucepan over medium-low heat.

Add onions and sauté the onions until the onions turn clear.

While sautéing the onions, add salt, pepper, thyme, and parsley.

Add chicken bouillon cubes and garlic to the onions. Stir to combine.

Add drained squash and diced cheese. Stir to combine.

Crumble cornbread into the squash mixture.

Pour the reserved cup of water in the pan and mix well.

Place the squash mixture in a 13 x11-inch baking pan that has been sprayed with a nonstick spray.

Cover the casserole and bake at 350 degrees for 50 to 60 minutes.

Remove cover in the last 20 minutes of baking time.