1 ½ to 2cupsfresh blackberries*see extra note on using frozen berries
For the Topping:
Combine all the ingredients in a bowl, mixing until there are large crumbs and no flour is visible. Refrigerate while continuing with the recipe.
For the Bars:
Heat oven to 350 degrees and line a 8x8 pan** with parchment, leaving two ends to hang over the sides.
In a mixer bowl, cream the butter, sugar and vanilla. Add eggs and beat well (it will be lumpy). Mix in flour, baking powder and salt well until everything is thoroughly combined. Spread dough evenly in lined pan.
Add a layer of blackberries over the dough. Top with the chilled crumb topping, being careful to leave lots of the large pieces intact to create a big crumb on the bars.
Bake for 40-45 minutes until golden brown.
Cool in pan before lifting out by parchment to cut on a board.
*This recipe works just as well with raspberries or blueberries, too.**You can use a 9x9 pan - the bars will be thinner and should bake in 35 to 40 minutes.Extra note for frozen berries: To use frozen berries, thaw the berries just a bit (not enough that they start producing lots of liquid - just enough to soften) and mix them with a tablespoon of flour. Sprinkle on top of dough as usual. Bake about 5 minutes longer than fresh.