Butter a 12-cup muffin tin well, being sure to butter the top of the tin as well so the muffin tops don't stick to the pan.
Whisk together the flour, baking soda, baking powder, salt and chia seed in a large bowl. In another bowl, beat the butter and sugar until light and creamy. Add the orange zest and, with the mixer on low, blend in one egg at a time. Add the vanilla. Blend in one-third of the milk, alternating with the flour mixture, until it's all incorporated. Do not overbeat.
Divide the batter among the muffin cups and then sprinkle with the streusel. Bake for 30 minutes or until a wooden toothpick inserted in the center comes out clean. Cool completely.
To make the glaze, whisk the powdered sugar with the orange juice, and let sit for a few minutes to thicken. Using a spoon, drizzle over the muffins.
Serve and enjoy.
In a medium bowl, make the streusel by mixing the flour, brown sugar, and salt. Cut in the 1-1/2 cups chilled butter using a pastry cutter. Refrigerate while you prepare the rest of the ingredients.
Orange Chia Seed Muffins with Streusel and Orange Glaze