In the food processor, chop the walnuts and add the steel cut oats. 

Transfer to a large bowl and add the chocolate chips.

In a small pan, bring to a simmer the maple syrup with the coconut oil and vanilla extract. After a few minutes, pour over the dry ingredients and mix with a spatula.

In a glass 8x8 baking dish, spread evenly to form a large square. Place in the freezer for about an hour. 

Remove from the freezer and slice them.