In a stand mixer, combine warm water (105-115°F) and sugar. Quickly whisk by hand until all sugar is dissolved. Add the instant yeast and again whisk until combined. Allow the yeast to sit for 5 minutes. If the yeast doesn’t bubble at all, scrap the recipe and start fresh (make sure yeast is fresh (not expired), this is the most important thing for a successful focaccia).
Place a dough hook on your stand mixer. Add the bread flour, all purpose flour, and salt to the mixer bowl. Mix until a sticky dough forms.
In a large mixing bowl, spread 2 tablespoons of olive oil around the sides of the bowl. Place the dough into the large bowl and use your hands to spread more oil on it. Cover the bowl with plastic wrap and place it near a window in the sun or another warm place for an hour (the direct warmth will help it rise).
The dough should have doubled in size. Use a silicone brush to spread 2 tablespoons of olive oil around 9x13 metal pan. Remove the dough from the bowl and place into the 9x13 pan. Fold it in thirds over itself a few times, flipping to ensure it’s well coated in oil & kneading slightly for better gluten development throughout.
Cover again with plastic wrap and let the dough rise in the sun or other warm spot for another hour.
When the dough has doubled in size and spread to the edges of the pan, remove the plastic wrap. Preheat the oven to 425°F. Pour the remaining 2 tablespoons of olive oil onto the surface of the dough and use your fingers to poke holes throughout the bread, you’ll want to see pockets and bubbles of bread before baking.
Use a spoon to spread ¼ raspberry jam onto the unbaked focaccia dough topping, ensuring it gets into the grooves you just created.
Bake for 18-22 minutes or until the top is lightly golden brown and cooked through.
Using a large straw, poke many holes into the bread (I did about 35 and that was the low end – don’t be shy, this is how the filling gets into the bread).
Using a small spoon, scoop the jam into each hole just created. The bread will warm the jam allowing it to drip into each hole.
Once slightly cooled, use an electric hand mixer to make the icing. Mix until icing is thin enough to be smoothed but thick enough to harden (add milk one tablespoon at a time to prevent from runny frosting). If time allows, once the top icing cools, flip the bread over onto a wire rack and frost the bottom (a true glazed donut!!!)
Cut into squares and serve!