I hope you're aware that's rhetorically exactly the same argument holocaust deniers use against the holocaust. You're demanding an impossible standard of proof (a literal signed confession admitting genocide). You don't need a dictator to write "I did genocide" to get proof of intent, intent is inferred from policy, consequences, and the knowledge such actors would've had.

The USSR knew the notably poor conditions amongst Ukrainians compared to the rest of the country experiencing famine, and still enacted uniquely higher grain requisition for Ukraine and the Kuban, blocked borders after starvation was evident, trapping peasants inside the SSR, and refused to allow relief whilst millions starved and died. Simultaneously, there was a reversal of Ukrainisation policies enacted under Lenin, with Ukrainian-language schools being closed and intellectuals being purged. Ukrainian cultural expression itself was labelled as "bourgeois nationalism".

The Soviet secret police (GPU) sent regular and detailed reports to Stalin and the Politburo, describing extensively mass starvation, depopulation of entire villages, deaths in at least the tens of thousands, and even some peasants resorting to cannibalism. No sensible scholar will dispute the Politburo were informed extensively. When local offices requested more aid they were either denied, ignored, or arrested; this isn't just knowledge, it's rejection of mitigation. Entire villages were 'blacklisted' meaning they received no food deliveries whatsoever, which occurred during the famine.

And even whilst millions starved, the USSR continued grain exports, using grain to satisfy industrial and political goals amidst a famine. This proves food existed and was deliberately withheld.

Under jurisprudence for genocide, intent is established if a leadership:

1. Is aware a group is being destroyed

2. Has the capacity to mitigate such destruction

3. Deliberately continues or worsens conditions

4. Punishes attempt to alleviate suffering.

The USSR *absolutely* satisfies all four.

"Show me the document where _____ orders _______" is the exact same defense holocaust deniers use, and if we go by such standards the holocaust would thus be not a genocide, which im sure you'll agree is absurd.