Embedding controllers into controllers

So I use a headless cms for some static page content, but some of the pages should have dynamic embeds like a price table that is based on stripe products.

So my content arrives as markdown like so:

Lorem ipsum dolor sit, ...
<div data-include="price_table"></div>

I use Floki to replace data-includes with another template

 Phoenix.Template.render_to_string(AlbumWeb.EmbedsHTML, include, "html",
  test: 20
)

However my problem is that I would much rather use a controller here, where I can do some business logic (like fetch the products) before rendering the template. (I tried using apply/3 for a dynamic invocation but it doesn’t work)

Or would there be an even better way like using smart page layouts?

To elaborate a bit further:

embed = apply(AlbumWeb.EmbedsController, String.to_existing_atom(include), [conn, %{}])

This somehow modifies the connection so that I lose the Lorem ipsum and I only receive the price_table markup