1. Have around 10000 mira.

2. Buy 99 each of Mature Cheese, Flaky Potato, and Coarse Rock Salt. You can quickly chose 99 to buy by pressing left.

3. Have Rean or preferably Juna cook 99 Chunky Potato Salad. This is the very first recipe.

4. Sell the dishes.

5. Repeat.

*If you don't have around 10000 mira, you can still do the process with less than 99 ingredients.

The cost of ingredients for a single dish is 100 mira.

Rean makes two dishes Pillowy Mashed Potatoes (sell value = 125, profit = 25) and Chunky Potato Salad (sell value = 100, profit = 0). So each Pillowy Mashed Potatoes will turn a profit of 25 mira. Chunky Potato Salad will not, but it won't lose you mira.

Rean usually makes around 78-93 Pillowy Mashed Potatoes. Let's assume he makes 85 dishes. This means (85 x 25) = 2125 mira profit.

Juna does the trick better, but she's not available immediately in the game. Unlike Rean, Juna's dishes Pillowy Mashed Potatoes and Crunchy Potato Croquette both sell for 125 mira, meaning 25 mira profit per dish. This will always give you (99 x 25) = 2475 mira profit.

It takes me 30 seconds for the entire process of buying ingredients, cooking, and selling. This is not including turboboost. So assuming you're using Rean, in five minutes, you can complete this process 10 times for (2125 mira x 10) = 21250 mira. Though, I recommend waiting until Juna is available.

Note that 21250 mira is alot in the early and mid-game.