With the dough hook attached, mix together the warm water, yeast, and brown sugar in the mixing bowl of a stand mixer. You can also mix by hand using a dough whisk and a large mixing bowl. Let the dough sit for 10 minutes to allow the yeast to proof/grow.
While the yeast is proofing, melt the peanut butter in the microwave for 30-45 seconds.
Add the salt, peanut butter, and flour to the yeast mixture and knead for about 5 minutes. Add the flour gradually, until the dough pulls away from the sides of the bowl and becomes tacky.
Cover the dough and let it rise for 1 -1 1/2 hours, or until it has doubled in size.
Mix together the fruit preserves and cornstarch in a small bowl.
Remove the dough onto a lightly greased surface and roll it into a rectangle about 9" x 15". Spread the fruit mixture on top of the dough, leaving about an inch around the edges. Roll the dough jelly roll style leaving the width of the dough 9". Pinch the ends together and slightly fold in the edges of the dough towards the seam to contain the fruit mixture.
Place the dough, seam side down, into a greased, regular size loaf pan. Cover and let it rise for 45 minutes or until the dough rises above the edges of the pan.
Bake at 350 degrees F for 15 minutes. After 15 minutes, cover the top of the bread with tinfoil and bake an additional 10-20 minutes, or until the internal temperature reaches 190 degrees F. Remove from the pan and if desired, melt 1/4 cup of peanut butter for 30 seconds in the microwave and drizzle on top. Slice and enjoy!