Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats to help the cookies bake evenly and prevent sticking.
In a medium bowl, whisk together the flour, rolled oats, brewer’s yeast, ground flaxseed, baking soda, baking powder, salt, and cinnamon (if using) until everything is evenly combined.
1 1/2 cups all-purpose flour, 2 cups old-fashioned rolled oats, 3-4 tablespoons brewer’s yeast, 3 tablespoons ground flaxseed, 1 teaspoon baking soda, 1/2 teaspoon baking powder, 1 teaspoon fine sea salt, 1 teaspoon ground cinnamon
In a large mixing bowl, beat the softened butter with the brown sugar and granulated sugar using a hand mixer or stand mixer on medium speed for 2–3 minutes, until light and slightly fluffy.
1 cup unsalted butter, 3/4 cup brown sugar, 1/2 cup granulated sugar
Add the eggs one at a time, mixing on low–medium speed just until combined after each addition. Scrape down the sides of the bowl as needed. Mix in the vanilla extract briefly until incorporated.
2 large eggs, 2 teaspoons pure vanilla extract
Pour the dry ingredient mixture into the wet ingredients. Mix on low speed just until the flour is mostly incorporated and no large dry patches remain. Avoid overmixing to keep the cookies tender.
Using a spatula, fold in the chocolate chips along with the nuts, shredded coconut, and chia seeds if using. The dough will be thick and slightly sticky.
1 1/2 cups chocolate chips, 1/2 cup chopped nuts, 1/4-1/2 cup unsweetened shredded coconut, 1/4 cup chia seeds
Cover the bowl and chill the cookie dough in the refrigerator for 30–45 minutes. This helps control spreading, deepens the flavor, and makes the dough easier to scoop. If you’re short on time, you can skip this step; the cookies may just spread a bit more.
Use a 1 1/2–2 tablespoon cookie scoop or a heaping tablespoon to portion the dough onto the prepared baking sheets, spacing the mounds at least 2 inches apart. For thicker cookies, leave the dough in tall mounds; for slightly thinner cookies, gently press down the tops.
Bake one sheet at a time for 10–12 minutes, or until the edges are lightly golden and the centers look just set but still soft. The cookies will continue to firm up as they cool, so do not overbake.
Let the cookies cool on the baking sheet for 5–10 minutes, then transfer them to a wire rack to cool completely. Serve once cool enough to handle, and store any leftovers as desired.