Drop this in lib/tasks/haml.rake and run rake haml:assimilate

haml.rake

namespace :haml do
  desc "Convert all .erb views to .haml"
  task :assimilate => :environment do
    git = File.exist?( Rails.root.join('.git') )

    chdir Rails.root do
      Dir["app/views/**/*.erb"].map do |file|
        [ file, file.gsub(/\.erb$/, '.haml') ]
      end.each do |(erb, haml)|
        sh "bundle exec html2haml #{erb} #{haml}"
        sh "git rm #{erb} && git add #{haml}" if git
      end
    end

    puts "All your erb are belong to us"
  end
end