Preheat the oven to 350°F. Grease a standard muffin tin with pan spray, making sure to coat the top of the tin as well. If desired, add paper liners (Note: do not use silicone liners, as the batter will bubble up at the sides, causing the streusel to sink into the middle.) Set aside.

Whisk flours, baking soda, baking powder, salt and chia seeds in a large bowl. In separate bowl, cream butter and sugar until light and fluffy. Add orange zest, and then add 1 egg at a time on low.

Mix together milk, orange juice and vanilla. Add to the butter-sugar mixture gradually in three parts, alternating with the dry ingredients, until just combined. Scrape down the sides and mix briefly to combine.

Fill muffins cups and top with a heaping tablespoonful of streusel, patting gently to adhere. Bake for 18–22 minutes, until light golden brown and a toothpick inserted in the center comes out clean. Cool for 10 minutes, then remove to a wire rack and cool completely.

Sprinkle cooled muffins with powdered sugar, a few sliced almonds and extra orange zest.

In a medium bowl, mix together flour, brown sugar and salt. Cut in chilled butter using a pastry cutter or two knives until the size of small peas. Refrigerate while you prepare the rest of the ingredients.