Add 100ml of the milk to a small bowl and sprinkle the yeast over the milk, allow this to sit for a few minutes before stirring to combine.
To a medium saucepan set over medium heat, add the remaining milk, sugar, and butter. Allow the butter to melt and the sugar to dissolve, then remove this from the heat and allow it to cool until just warm.
Add the beaten eggs to the butter and milk mixture and stir to combine.
Sift together the bread flour and the salt, and set aside.
Add the activated yeast mixture to a bowl of an electric mixer fitted with a paddle attachment. Add half of the dry ingredients and mix briefly, then add the warm milk and egg mixture and mix until a loose dough forms.
Change the mixer’s attachment to a dough hook attachment and with the mixer’s motor running at medium speed add the remaining flour mixture one large spoonful at a time until a soft dough forms.
Change the mixer’s attachment to a dough hook attachment and with the mixer’s motor running at medium speed add the remaining flour mixture one large spoonful at a time until a soft dough forms.
Once all the flour has been added, increase the speed of the mixer to medium-high and leave the dough to knead for about 10 minutes. The dough is ready when it is smooth and springs back gradually when pressed. The dough should be soft but not too sticky, if it’s very sticky add 1 tablespoon of flour to the mixture and mix, if the dough is too hard add 1 tablespoon of milk. Check the consistency from there.
Transfer the dough to a large glass bowl brushed with melted butter, cover the bowl with a tea towel, and allow the dough to rise for about an hour to an hour and a half, or until it has doubled in size.
Once the donut dough has risen, remove it from the buttered bowl and place it onto a lightly floured surface. Roll out the dough using a rolling pin into a large rectangle with a thickness of about 1.5cm (½ inch) throughout.
Use a round 7cm (3 inches) cookie cutter to shape each donut and place them onto a large baking sheet lined with parchment paper. Gather and knead the remaining dough, then roll and shape with a cookie cutter.
Cover the oven tray with a clean kitchen towel or plastic wrap and allow the donuts to rise for a further 30 to 45 minutes in a warm place.
Set a large heavy-bottomed pot over high heat and fill the pot with oil until it is about 10cm (4 inches) deep, heat the oil until it is about 170C (340F).
Use scissors to cut squares out of the baking paper that the donuts sit on, lift the paper with the donut on it, and tip it carefully into the hot oil. Fry the donuts for about a minute on each side until golden. Lift them out of the oil with a slotted spoon and place them onto a plate lined with an absorbent paper towel.
Use a fine grater to grate the dried strawberries into a small bowl, add the castor sugar, and stir to combine. While the donuts are still warm roll them into this sugar mixture.
Fill a piping bag with the strawberry jam. Use a sharp knife to pierce a hole into one side of the donut, and fill this hole with the jam. Serve and enjoy!