If I may bump this issue, I have encountered the same set of circumstances.
I have a fresh installation of macOS 10.12.2; Installed both laravel/installer and laravel/valet. The composer.phar is installed in the /usr/local/bin/directory. I have created an alias to run composer.
composer is aliased to `php /usr/local/bin/composer.phar'
laravel new blog
generates this response
sh: composer: command not found
Application ready! Build something amazing.
The site does not run. In order to get the site to work, I had to run these additional steps:
composer install —no-scripts
cp .env.example .env
php artisan key:generate
If I create the site using composer, the site works as expected.
composer create-project --prefer-dist laravel/laravel blog
I am fairly certain that the error from composer: command not found is where .env file is created and keyed. It is also where the dependancies are installed. Does anyone have thoughts on where to begin to troubleshoot this?