I assume you've figured this out already, but if you haven't...I'll change this back in the next update and see if there is another way to disable the default recipe. I didn't expect it would completely remove the block from the world.
If I remember how minetweaker works, you should be able to really easily change the recipe with it:
recipes.remove (/* Whatever the Infuser's ID is */ ) <-- Removes all ways to craft that item, including default
recipes.addShaped( /* New recipe */ ) <-- Adds in a new recipe (is ran after all recipes are deleted, so it will be the only one)