Cook the potatoes in a saucepan of salted boiling water for 5–6 minutes until softened. Drain and leave to cool.
Heat a dry frying pan and fry the bacon until golden and crisp. Leave to cool.
Mix together the flour, baking powder, chopped thyme and a little salt and pepper in a bowl. Stir in the potatoes and bacon. Beat together the milk, oil and egg in a jug. Add to the dry ingredients and stir together using a large metal spoon until just combined.
Divide the mixture evenly between paper muffin cases arranged in a 12-hole muffin tray. Sprinkle with a little salt and scatter with thyme. Bake in a preheated oven, 220°C (425°F), Gas Mark 7, for 15–20 minutes until risen and golden. Transfer to a wire rack to cool. Serve warm or cold, scattered with extra thyme sprigs.