Combine warm water and sugar in a bowl, stir until dissolved, then sprinkle yeast on top and let sit until frothy.

Mix the yeast mixture with bread flour, all-purpose flour, and salt in a stand mixer using a dough hook on medium speed until a sticky dough forms.

Grease a large bowl, transfer dough, coat with olive oil, cover, and let rise until doubled, about 1 hour.

Grease a 9x13-inch pan, punch down the risen dough, transfer it to the pan, spread evenly, cover, and let rise for another hour.

Preheat oven to 425°F while the dough rises.

Poke holes in the risen dough, spoon jam over the surface, and let some seep into the holes.

Bake for 18-22 minutes until golden brown.

Whisk confectioners’ sugar with milk in a bowl until smooth for the glaze.

Cool focaccia slightly, glaze the top, slice into squares, and serve warm.