どんなに～ても・
どんなに is "how" and いくら is "how much". In front of a ても sentence they turn "even if" into "no matter how": however far it goes, the result is the same.
No matter how busy I am, I always eat breakfast.
No matter how many times I explained, he wasn't convinced.
How to form it
どんなに／いくら + adjective or verb + ても／でも
どんなに寒くても, いくら待っても, どんなに便利でも. What goes in between can be more or less: how cold, how long you wait.
In use
What follows is what stays the same. Often it is a complaint that nothing works, or a promise that nothing will stop you.
No matter how much we hurry, we won't make the last train.
I never get tired of this song, no matter how many times I listen to it.
No matter how cold it is, this dog wants to play outside.
どんなに or いくら?
Usually either will do. どんなに comes more easily with how something is or feels: どんなに寒くても, どんなに好きでも. いくら comes more easily with how much or how many times: いくら食べても, いくら呼んでも.
However hard I try, I can't beat my older brother.
However hard I try, I can't beat my older brother.
Both are natural, and they mean the same.
どんなに, not どんな
Whatever the problem, she thinks it through calmly.
どんな goes with a noun: any problem at all.
No matter how difficult the problem is, she thinks it through calmly.
どんなに goes with 難しい: however difficult.
With no noun there, only どんなに works: どんなに忙しくても, not どんな忙しくても.
Close neighbours
ても・でもN4
The other question words work the same way: 何を～ても (whatever), いつ～ても (whenever), だれが～ても (whoever).
At this restaurant, whatever you eat is delicious.
たとえ～てもN3
"Even if": one supposed case, not every degree of something. It only supposes, where いくら～ても can also tell what really happened.
Even if it rains, the match will go ahead as scheduled.
たってN3
In casual speech the ても becomes たって.
No matter how many times I explain it, he won't change his mind.
Check yourself
1Which one fits?
（ ）
Choose an answer to see why.
2Which one fits?
いくら
Choose an answer to see why.
More detail
いくら also goes straight before a noun: いくら子どもでも, "he may be a child, but even so". いくら何でも is a set phrase for something that goes too far.
Whichever way you look at it, that's too expensive.
どれだけ is used the same way: どれだけ頑張っても.
More sentences
No matter how much money you have, you cannot buy time.
However bad the conditions are, with a little ingenuity you can find a way.
However much more of the ingredients I added, the flavor didn't get any stronger.