Prepare the Buttery Biscuit Crumble Topping:
In a medium bowl, whisk together flour, sugar, baking powder and salt until well combined. Using a pastry blender or a fork, cut butter into flour mixture until it resembles a coarse meal with small pea-sized pieces of butter. In a small bowl, whisk vanilla into beaten egg replacer using a fork. With a fork, gently toss beaten egg replacer mixture and vanilla into flour mixture until moistened and dough starts to hold together. Continue to toss and blend gently with fingertips until well combined, yet taking care not to overwork the dough.