I'd go with more random.
Master Chef: feat. You gain proficiency with chef's tools. If you are already proficient in chef's tools, you instead gain expertise.
During a long or short rest you can consume purchased or fresh foraged ingredients to either invent a recipe, practice a recipe, or reproduce one you have mastered.
You can have as many recipie's mastered at one time as you have proficiency bonus. If you want to try to master another recipie, you must forget one of the one's you have mastered.
All recipe's have key ingredients. Exotic or high quality ingredients can grant a bonus to your check. You cannot benefit from a specific bonus again until you take another long rest, and bonuses that grant lasting effects last until you take another rest.
Invent a Recipe:
Start with a key ingredient. Higher quality ingredients give a bonus to this and later checks.
15+: food is edible
20+: roll once on the bonus table
25+: roll twice on the bonus table, pick either
Practice a Recipe
Requires the key ingredients for the recipe.
10+: Food is edible, but no bonus.
15+: Successfully reproduced, give bonus.
20+: Recipe is mastered. Roll once more on the bonus table and add it to the meal's effects.
25+: Recipe is mastered. Roll twice on the bonus table, and pick either.
Reproduce a Mastered Recipe:
Requires the key ingredients for the recipe.
10+: Food is edible, but no bonus.
15+: Successfully reproduced.
Bonus Table
1: Gain 1 Temp HP per character level
2: +5 foot speed
3: Regain 1 HD.
4: Gain 1d4 you can spend once to gain a saving throw bonus once as a reaction to the roll
5: Gain 1d4 you can add to an attack/damage roll once as a reaction to the roll
6: Gain 1d4 you can add to an attribute check once as a reaction to the roll
7: Gain 1d4 you can add to your AC to avoid an attack once as a reaction to the roll
8: As a bonus action, remove disadvantage on one attack or ability check on your turn.
9: Any HD that rolled an even value that where spent during this rest are not expended.
10: Heal 1 point of ability damage, if any.
11: Spicy! As a reaction to taking fire damage, you can gain resistance against the damage. (special ingredients could change the type of damage you gain resistance from here)
12: Satisfying. Your next short rest takes only 10 minutes.
So mastered recipes have two effects on the above table.