Preheat oven to 350 degrees F.
In a large bowl, combine oat flour, gluten-free flour, sugar, baking soda, baking powder, and salt. Mix well.
If you have a food processor, pour dry ingredients into a food processor, and add in the cold butter and pulse a few times until ingredients start to clump together.
Pulse in the vanilla, yogurt, egg yolk, and chocolate chips until just combined. Do NOT over mix.
Transfer dough to a surface dusted with gluten-free flour. Knead very gently until dough starts to form a ball.
Gently pat the dough down to 3/4" thick. Cut dough into 12-16 equal size pieces.
Carefully move the pieces to a baking sheet lined with parchment paper.
Brush each bar with a bit of half and half, and sprinkle with coarse sugar if desired.
Bake for approximately 16-20 minutes or until bars are lightly browning and spring back when touched.
Remove from oven and let cool completely.