To make blueberry bagels, combine a 3/4 cup of warm water, 100 grams of thawed frozen blueberries, two teaspoons of dry yeast and two tablespoons of caster sugar. Let it sit for five minutes or until the mixture becomes frothy. Combine 2 1/2 cups of plain flower, 1 teaspoon of ground cinnamon and 1/2 teaspoon of salt in a large bowl. Make a well in the center.
Pour the blueberry and yeast mix into the well. Stir until the mixtures come together.
Lightly flower a clean surface and knead the mixture until the dough becomes smooth and elastic. Let it rise to double its size or for 30 minutes by placing the dough in a large bowl. Cover the bowl loosely with plastic wrap.
Preheat the oven to 180 degrees Celsius or 356 degrees Fahrenheit. Divide the dough into eight even portions and roll each into a ball. Flatten the dough balls slightly and place them on an oiled tray. Let them rise for 10 minutes.
Boil water and caster sugar in a large saucepan over high heat. Then simmer by lowering the heat to medium.
Add four bagels to the simmering sugar water and allow to cook for three minutes. Turn them over and let them cook for three more minutes. Remove bagels from the water, place them on the oiled tray and repeat with the remaining four.
Brush each bagel with a mixture of egg yolk and milk, and sprinkle with sugar. Bake in the oven for 20 minutes or until golden brown and cooked through. Remove the bagels from the oven and let them cool before serving.