Preheat the oven to 350 degrees and prepare a doughnut pan with cooking spray or butter.
In a large bowl, whisk together the flour, baking powder, salt and sugar.
Add the milk, egg, melted butter and strawberry jam and mix until well incorporated.
Gently fold in the diced strawberries.
Distribute the batter evenly among 12 doughnut molds, being careful to leave the centers exposed.
Bake for 10 minutes or until lightly golden. Turn the doughnuts out onto a baking sheet and allow to cool.
Meanwhile, prepare the glaze by whisking together the confectioners sugar, whole milk, strawberry jam and strawberries.
When the doughnuts are cooled, dip each doughnut in the glaze and allow to set before serving.
You can adjust the thickness of the glaze by adding more or less powdered sugar. The consistency of your glaze may vary depending on the moisture content of the strawberries. So you may need to play around and adjust accordingly.