What can I use instead of powdered milk to turn dark chocolate into milk chocolate? I am a chocolate lover and recently figured out I have to completely remove milk from my diet (due to problems with casein). I figured I can make my own milkless milk chocolate from dark chocolate by adding soy milk and... thickening it all the way back to solid form.

Now the problem is normally the way I'd approach it would be adding parts of liquid milk and parts of powdered milk to end up with good enough consistency for a chocolate block.

But I can't use powdered milk for the same reason I can't use liquid milk. I realize there are vegan alternatives to powdered milk like soy powder or coconut powder but those are really hard and expensive to get in Poland.

What can I use or do to create my own milk chocolate from dark chocolate with easily purchasable ingredients?
Milk chocolate is made with powdered milk; adding a liquid will make it break or it'll be unable to set. If you add something with enough fat to keep it from breaking, like coconut milk, you'll end up with a delicious chocolate ganache, but it won't set like a chocolate bar. I would instead look for a vegan milk chocolate; some companies are making them with coconut milk solids. You may have to order them online.