Preheat the oven to 220°C (425°F /Gas mark 7). Place the herbs in the food processor and pulse to roughly chop them. Add the beef mince and whizz together to combine. Season and mix. On a lightly floured work surface, cut the pastry in half vertically so that you have two rectangles - 12cm (4½ inches) x 35cm (14 inch) rectangles.
Divide the meat filling in half. Spread each rectangle with the meat filling, leaving 1 cm (½ inch) border all the way round the edge. Bring the edges together and pinch tightly giving a curvy seal.
Line a baking tray with nonstick baking paper. Glaze the pastry with the beaten egg yolk and sprinkle with sesame seeds. Cut each rectangle into approximately 15 slices. Bake for 15 minutes or until golden brown and crispy. Ensure meat is cooked with no pink showing.
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