Preheat the oven to 350 degrees F and line a 9" x 5" loaf pan with parchment paper (or spray with cooking spray).: When your oven reaches 350 degrees F , you should feel a steady heat when you open it and smell a faint warmth. This even heat ensures the edges and center bake at similar rates. If the oven is underheated, the brownies may stay too moist and sink. A quick oven thermometer check can prevent this common pitfall.
Start by preparing the flax "eggs." Stir together the ground flax seed and water together in a small bowl. Allow mixture to sit, stirring occasionally, until thickened and the consistency of beaten eggs, about 15 minutes.: You will notice the mixture transform from watery to glossy and gelatinous, with a slightly nutty scent. This thickened texture is what gives structure when eggs are omitted. If you skip resting, the batter will be looser and the final texture might be crumbly or fail to bind properly.
Transfer the flax "egg" mixture to a stand mixer, along with the almond butter and coconut oil. Beat until well-combined and creamy. Add the remaining ingredients (except chopped candy canes) and continue beating until well-combined. The batter will be thick and slightly crumbly - this is normal.: As you beat, watch the mixture become smooth and glossy, with faint streaks disappearing. The almond butter and coconut oil should emulsify into a creamy matrix that carries the dry ingredients. If the batter appears too dry, it likely needs a bit more mixing to incorporate the fats; avoid adding extra liquids which would change texture.
Transfer the brownie batter to the prepared loaf pan and smooth into an even layer. Sprinkle with chopped candy canes (if desired). Bake on the center rack of the preheated oven for 25 to 35 minutes, until set up and brownies are cooked to desired doneness (for fudgier brownies, bake 25 minutes, and for cakier brownies, bake 30 to 35 minutes).: At this point you will feel a dense, almost dough like batter, and it may stick to your spatula. The batter should not be runny, because that density translates into fudgy brownies after baking. Overmixing can result in a drier crumb, so stop once everything is evenly moistened and you see streaks disappear.
Remove from the oven and allow brownies to sit for 30 minutes before pulling on the parchment paper and releasing them from the loaf pan. Sprinkle with sea salt (if desired), cut into squares, and enjoy.: Smooth the top with a spatula until even, which promotes uniform baking and predictable slices. The surface should look matte and compact. If you pack it too tightly, the center may take longer to set; if you leave peaks, you will get uneven browning.
Bake on the center rack of the preheated oven for 25 to 35 minutes, until set up and brownies are cooked to desired doneness (for fudgier brownies, bake 25 minutes, and for cakier brownies, bake 30 to 35 minutes): During baking you will smell rich chocolate filling the kitchen and see the edges pull away slightly from the pan. The top may crack a little, which is a good sign of proper rise. Press gently at the center when near the shorter time, and if a few moist crumbs cling it is fudgy; if it springs back it is cakier. Avoid opening the oven repeatedly, which causes temperature drops and uneven set.
Remove from the oven and allow brownies to sit for 30 minutes before pulling on the parchment paper and releasing them from the loaf pan: As the brownies cool, the residual heat finishes setting the interior. You will notice the scent settle from hot chocolate steam to a warm, concentrated aroma. Cutting too soon leads to messy slices that crumble; patience yields cleaner squares and a firmer texture.
Sprinkle with sea salt (if desired), cut into squares, and enjoy: The final touch of sea salt brightens flavors and accentuates the chocolate and peppermint. When you slice, the knife should glide through with slight resistance and reveal a glossy interior if fudgy. A common mistake is using a dull knife which tears the slice, so run the blade under hot water and dry it for cleaner cuts.