Preheat a griddle. In a large bowl, whisk together dry ingredients. Slowly mix in egg, milk, peanut butter and oil until combined. Add a little extra milk if batter feels too thick. Let mixture sit 5 minutes. Melt 1 tablespoon butter on griddle and move around to coat entire griddle. Pour about 1/4 cup of batter per pancake on griddle to form 5-inch pancakes. The batter spreads as it cooks. Fill griddle without crowding pancakes. Flip when air pockets start to pop on the top and a quick peak on the underside reveals a golden pancake. Repeat with remaining butter and batter. Serve pancakes with Blackberry Syrup.
In a saucepan over medium heat, combine all ingredients and bring to a boil, stirring until sugar is dissolved. Lower heat to a simmer and cook until liquid is reduced to a syrupy consistency, about 10 minutes. Use a wooden spoon to break up blackberries as they cook. Strain syrup to remove seeds and serve warm.