Preheat the oven to 190°C.

Add sweet potatoes to a saucepan of boiling water.

Simmer uncovered over medium heat for 6 minutes.

Add squashes and simmer for 4 minutes, or until both vegetables are nearly tender but not too soft.

Drain and rinse the vegetables with cold water.

Cut squashes and sweet potatoes into 2 centimeter dice.

Heat the oil in a medium saute pan.

Add onion, pepper and celery and cook over medium low heat, stirring, until onion begins to brown, about 7 minutes.

Add garlic and cook for another 1/2 minute.

Add the tomatoes, bay leaf, paprika, salt and pepper and bring to a boil.

Cook uncovered over medium heat, stirring often, for 10 minutes or until the sauce is thick.

Discard the bay leaf.

Add the oregano, thyme and hot sauce to taste.

Add the squash, corn and sweet potatoes to the sauce.

Season to taste with salt and pepper.

Spoon into a 2-liter casserole.

Cover and bake for 25 to 30 minutes or until the vegetables are tender.