In a stand mixer, combine warm water and sugar. Whisk until dissolved, then sprinkle in active dry yeast and let sit for about 5 minutes until frothy.

Mix in bread flour, all-purpose flour, and salt, then beat on medium speed for about 3–5 minutes until a sticky dough forms.

Transfer dough to an oiled bowl with olive oil, cover with plastic wrap, and let rise in a warm area for about 1 hour.

Grease a baking pan with olive oil, punch down the dough, transfer it to the pan, fold a few times, cover with a towel and let rise again for 1 hour.

Preheat oven to 425°F about 15 minutes before baking. Poke deep dimples into the dough and spread a layer of raspberry preserves over it.

Bake for 18–22 minutes until golden brown. The focaccia should look light and airy.

Cool for 5 minutes, poke holes into the bread, and fill with more raspberry preserves.

Mix confectioners' sugar with whole milk to make glaze, spread it over the focaccia while warm, and enjoy.