How to capture EE embed output with Stash variable?

I have an EE embed that processes PHP code. I would like to capture that output with a Stash variable.

I'm using a model/view approach, ie. have one template to retrieve the data and another to output the page.

I have this code working correctly in my model:

{exp:stash:set name="my_var"}
    {embed="resources/store-post-data"}
{/exp:stash:set}

<h2>Test</h2>
{exp:stash:my_var}

and get results as expected:

Test
MyPostParameterValueHere

But when I use the exact same code

{exp:stash:my_var}

in my view I get the string

{embed="resources/store-post-data"}

and not the output of the embed.

What am I missing?