My question is derived from a few contradicting pieces of information but I have no direct answer with an example. I'll first describe the information:
Goodberry, has no cast at higher level footnote in its description:
Up to ten berries appear in your hand and are infused with magic for the duration. A creature can use its action to eat one berry. Eating a berry restores 1 hit point, and the berry provides enough nourishment to sustain a creature for one day.
The berries lose their potency if they have not been consumed within 24 hours of the casting of this spell. (P. 246 PHB)
The rules of casting a higher spell level for a spell with no higher spell level footnote say:
When a character casts a spell, he or she expends a slot of that spell’s level or higher, effectively “filling” a slot with the spell. You can think of a spell slot as a groove of a certain size—small for a 1st-level slot, larger for a spell of higher level. A 1st-level spell fits into a slot of any size, but a 9th-level spell fits only in a 9th-level slot.
Now the Contradicting:
From Disciple of Life (Cleric):
Also starting at 1st level, your healing spells are more effective. Whenever you use a spell of 1st level or higher to restore hit points to a creature, the creature regains additional hit points equal to 2 + the spell’s level. (emphasis added)
And Sage Advice:
If I’m a cleric/druid with the Disciple of Life feature, does the goodberry spell benefit from the feature?
Yes. The Disciple of Life feature would make each berry restore 4 hit points, instead of 1, assuming you cast goodberry with a 1st-level spell slot.
So The first part tells me I could use a Level 2 spell slot on a 1st level spell that does not have a empower spell footnote and the spell will be cast at the description of the spell and no more.
The contradiction of the Sage Advice says assuming they use a level 1 spell slot. And the Life cleric says 2+ spell's level.
Does this mean a Level 1 Spell Slot Goodberry gives 1hp per berry + 2hp Life Domain +1 Spell Level = 4 hp per berry, and a Level 2 Spell Slot 1hp per berry + 2hp Life Domain +2 Spell Level = 5 hp per berry?
Or because the Life Domain clause doesn't say + Spell Slot level and only Spell level, that a Life Domain Cleric's Goodberry never gets higher then 4hp per berry?
Best Answer
Yes!
This is a very interesting synergy that is viable.
Disciple of Life states:
If we start with the Sage Advice that Disciple of Life applies, emphasis mine:
The implication is that if you were to use a higher level spell slot you could increase the potency. Otherwise, they'd have made it a full stop at 4 HP/Goodberry. By including "assuming...with a 1st-level slot", they are clearly saying that if you use a higher level slot, you'll have increased HP on the goodberry.
Upcast is based on Disciple of Life
It doesn't matter that Goodberry doesn't have any upcast rules - what matters is that Disciple of Life DOES. By using a higher level spell slot, you are utilizing that ability to increase the potency. The term "spell's level" is determined by the level it was cast at - not the base level.