Preheat the oven to 180°C/350°F/gas 4 and line a 23cm square brownie tin with greaseproof paper. Sift together the flour, baking powder and sea salt into a bowl. Split the vanilla pod lengthways and scrape the seeds into a large bowl. Add the soya yoghurt, honey and sugar, and mix until well combined. Gently fold the dry ingredients into the wet ingredients. Roughly chop the chocolate and fold in. Pour the batter into the prepared brownie pan and evenly spread over the pan with a spoon or spatula. Bake in the oven for 30 to 35 minutes, or until the top of the blondie is firm and brown. Let the blondie cool completely in the pan. Cut into 12 pieces and serve.