Learn all the recipes

You could use the cheat to max the Sims skill in cooking, gourmet cooking, and baking. Although this wouldn't teach them the recipes they would learn from trying foods from food stalls.

Edit:
Here are the cheat codes if you need them:

Cooking:
stats.set_skill_level Major_HomestyleCooking 10

Gourmet Cooking:
stats.set_skill_level Major_GourmetCooking 10

Baking:
stats.set_skill_level Major_Baking 10