Combine 1 cup flour, undissolved yeast, sugar and salt in a large bowl. Add very warm water, vanilla extract and butter; mix until well blended, about 1 minute. Gradually add enough remaining flour to make a soft dough. Dough should form a ball and will be slightly sticky. Knead on a floured surface, adding additional flour if necessary, until smooth and elastic, about 4 minutes. Just prior to finishing kneading, add in miniature chocolate chips. Allow dough to rest for 10 minutes.