Preheat oven to 350 degrees F.
In a stand mixer bowl, add the warm water, yeast, and sugar. Allow to sit for about 5 minutes, or until bubbly.
Add the avocado oil and about 3½ cups of einkorn flour and mix on low for about 2 minutes. Add the last cup of flour about 1/4 cup at a time, just until the dough pulls away from the sides of the bowl and isn't sticky (you want to add enough flour so your dough is firm enough to hold a shape but still soft).
Gently place a kitchen towel or plastic wrap over the dough and let it rise for about 15 minutes, or until doubled in size.
Transfer the dough to a lightly floured surface and roll out into a rectangle that is about 1/3"-1/2" thick. Brush with melted butter, then sprinkle the brown sugar and cinnamon over the top.
Cut into 1" strips and twist the breadsticks. Lay on a greased cookie sheet, then sprinkle again with ground cinnamon. Let sit for 15-20 more minutes, or until double.
Bake in the preheated oven for about 15-18 minutes, or until golden.
While the breadsticks are baking, whisk together the powdered sugar, milk, and vanilla in a small bowl. Once the breadsticks have baked, remove from the oven and let cool for 5 minutes, then drizzle the glaze over the top.
Serve immediately or store in a freezer bag or another airtight container. Enjoy!