Prakriti's P.O.V,
"Is milk delicious"
...
When Karna heard this question of Ashwatthama, despite knowing his story from his previous lives, he couldn't help but doubt his sentience.
Ashwatthama, the warrior born after merging the individual forces of Lord Shiva, namely Yama (Death), Kama and Krodha (Fury).
The embodiment of strength itself, a born warrior!
The true slaughterer who had almost wiped the whole army of Pandavas! The almost invincible being and an avid devotee of Lord Shiva.
Despite getting a perfect body, making him the most fearsome warrior in the three realms (Below the Trimurtis), by simply existing in the universe, A true protagonist with the ultimate cheat-The Almighty Gem!
Therefore, when a warrior of this caliber asked a childish question, Karna was dazed for a while.
However, It doesn't mean that Aswatthama is perfect. Despite the great blessings of Lord Shiva, There's a single problem with him, he got all those powers due to his father's efforts. Additionally, he couldn't keep them under his control. Most of the time, his power influences him to do the unthinkable, as proved from his previous Niyati.
He acquired the powers of Lord Shiva but neither his spirit nor his wisdom. Instead of controlling Krodha (Fury) as his strength, he was played like a fool by his own power. It can be observed from his actions of joining Duryodhana's side at the great war of 'Mahabharata' rather than the Pandavas, when they were the ones who crowned him the king of half of Panchal kingdom, it clearly shows his clouded judgement.
Additionally, he indiscriminately used Narayana-Astra and Brahma-Astra on normal soldiers and Uttara's womb, indicating his lack of control on his own power of Krodha (Fury).
His inability to control his own powers were the real reason for his fall and being cursed by Shri Krishna.
With the three mighty powers on the gem, Surely, he will become one of the strongest warriors but his end won't be good.
His whole life is the prime example of 'What a lack of wisdom and control can do.' Even someone born with the strength comparable to Lord Shiva fell because his inner self was unstable, similar to Karna.
Though Karna is in the possession of great knowledge from his previous lives, he couldn't use them. He was hiding from his own memories, overwhelmingly disgraceful for any warrior!
But, Ashwatthama's problem can be solved with proper knowledge and manners. It's not that Devi Kripi didn't teach him any of these, rather she taught him well. It's just, he was unaware of his own powers until the death of Acharya Drona.
Both are the heroes pitied by the masses...
The heroes born with an adverse destiny...
The Ones who fell due to their past mistakes...
The Ones, who were unable to find their real self...
...
...
After recovering from his momentary shock, Karna answered Ashwatthama's question, "Yes, Milk is very delicious."
Hearing Karna's answer, Ashwatthama hesitated for a second before asking again, "Karna, can I ask you one more thing?"
"You can." Karna replied as sat beside Ashwatthama and sprinkled some of the flowing water of Triveni Sangam on his head as their blessing before he dipped his feet into it. Following which, he turned to Ashwatthama, who was trying to gather his words while Karna enjoyed the cool sensation of the gentle caressing that is being done by the Mid-night water.
"Actually Karna, I want to taste milk, but... Our financial condition isn't good. So... I don't know if I should ask Maa (Mother) to buy it for me or not? In reality, I don't want to make things more difficult for her..."
Ashwatthama laid his true feelings bare before Karna, A strange whom he didn't know much about and yet, he felt some kind of link between themselves.
A kind of feeling, different from the other kids at the Ashram, he felt somehow connected to him. Don't know whether this feeling originated from their similar destinies or his powers belonging to the same origin as that of Karna. (i.e. Maa Shakti)
{Note: Lord Shiva and Devi Parvati's form of Adi shakti is the closest form to that of Maa Shakti. That's why the Ashwatthama might have felt a connection with Karna in this story and Duryodhana in 'Vijaya Samhita' as Duryodhana was also born from the boon of Lord Shiva.}
Karna didn't stop Ashwatthama to let his worries out. Ashwatthama presented his dilemma before Karna, hoping to find a solution to his problem.
However, Instead of giving him any direct answer Karna asked him, "Who are you?"
Not ready for this question, Ashwatthama was confused for a bit before he answered in a firm tone, "Me?... I'm Ashwatthama, the son of Shri Drona and Devi Kripi, A Brahmin from birth."
Hearing his reply, there wasn't a single change in Karna's expression as he asked again while gazing at the sky filled with countless stars, "What do you desire?"
"...I really want to taste milk..." After hesitating for a little, Ashwatthama gave his response as he too looked at the beautiful night view.
...
Both of them gazed at the stars, creating a wonderful scenery of two children with divine appearance gazing at the sky, until Karna broke the silence as said, "Ashwatthama, I have two solutions for your problem."
"First, As a Brahmin, Your father, Shri Drona, can only provide you with the things he acquired from Alms. You can be an obedient son and be satisfied with what you have by following the teachings of Maa Santoshi (Goddess of Satisfaction). It is your father's dharma to not desire anything more than he is offered. Even though your desire is purely out of harmless curiosity, it can potentially influence him to do something he shouldn't."
"Second... This world is for everyone. The Kshatriyas, The Brahmins, The Vaishyas, and The Sutas, these varnas are only the reflection of an individual's characters. It doesn't matter which of them you want to be. The Sacred Vedas never discriminated between us. If your family's financial condition isn't good, You can earn what you want. If You are capable, wise and brave, nothing can stop you from achieving what you desire!"
"Why beg from others? Didn't the supreme have said that No one gets anything for nothing. One has to do the work/Karma equivalent to have what he wants. He never forces others. We get what we work for. Dronacharya ji are following their own dharma of being a brahmin. As for you..."
After speaking for so long, Karna broke his gaze away from the sky and looked straight into the dark irises of Ashwatthama before he asked, "That only question is... What is it you truly desire?..."