Preheat oven to 400°F (200°C). Line rimmed baking sheet with parchment paper.
In food processor, purée basil, peas, garlic, oil, lemon juice, ¼ tsp (1 mL) salt, and pepper until smooth. Transfer to bowl; whisk in egg and ½ cup (125 mL) buttermilk.
In large bowl, stir together flour, baking powder, remaining salt and ¾ cup (175 mL) Parmesan; using fork or pastry blender, work in butter until crumbly. Pour in egg mixture; stir until just combined (mixture should look moist).
Turn onto floured surface; divide dough in half. Gently form each half into a ball and pat into 6-inch (15 cm) round. Cut each round into 6 wedges. Place wedges on prepared baking sheet and brush with some of the remaining buttermilk. Sprinkle remaining Parmesan over top. Bake in centre of oven for 16 to 18 minutes or until lightly golden brown. Serve warm.
Tip: Blend peas with ¼ cup (60 mL) prepared pesto for a time-saving hack.