Heat oven to 350 degrees F. Line a 12-count standard muffin tin with paper liners.

To make the topping: in a small bowl, combine the 1/4 cup flour blend, 1/4 cup sugar, cinnamon and nutmeg. Add the butter and work it into the flour-sugar mixture with your fingers until small crumbles form.

Lightly beat the eggs in a large bowl. Stir in the oil, milk and blueberry oil (if using). To measure the flour, lightly spoon into measuring cup and level off with the back of a knife or weigh with a kitchen scale. Add the 1 1/2 cups flour blend, 2/3 cup sugar, baking powder and salt to the egg mixture. Stir until smooth. Gently fold in the blueberries.

Fill each muffin cup about 2/3 full. Sprinkle the topping mixture on top, evenly distributing. Bake 22 to 25 minutes, or until muffin tops spring back when lightly touched. Cool and serve.