Boss Rush mode is the best way to earn Desserts quickly. However, you'll still need to finish story mode once to unlock that mode. This method is applicable for players going through Story Mode for the first time.
Here’s a reliable method in farming Dessert Points and randomly generate weapons add to your collection. Take note that the weapon quality will depend on the stage. The last stage will always have the chance to spawn Rank A to Rank S weapons.
Continue with your normal gameplay until you reach the 4th act/level of the current area you're in. (1-4, 2-4, 3-4, 4-4) From there, finish off the boss, collect the weapon and dessert it drops.
Proceed to the end room to loot more chests. Buy new weapons from the shop as well.
Don’t proceed to the portal; instead, suspend your game and return to the main menu.
Continue your suspended game and you’ll start off in the 4th level. Defeat the boss again, and repeat the process. Take note that the weapons you’ll get will depend on the weapon types you have already unlocked.