Put the quark, milk, oil, salt, sugar and egg into a mixing bowl. Mix flour and baking powder. Mix half with the quark mixture. Fold in the remaining flour with the dough hooks of the hand mixer. Wrap in foil and chill briefly.
In the meantime mix poppy seeds and chopped almonds. Roll out the dough into a rectangle (30 x 40 cm) on a lightly floured work surface. Divide the dough into thirds lengthwise. Divide the poppy seed mixture into thirds, spread on the strips, leaving a narrow edge all around. Press the edges of the dough together to form 3 rolls. Weave the dough rolls loosely. Place the braid on a baking tray lined with baking paper. Spread butter in flakes on the plait. Sprinkle with flaked almonds. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 55 minutes.
Place the braid on a baking tray lined with baking paper. Spread butter in flakes on the plait. Sprinkle with flaked almonds. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for about 55 minutes. If necessary, cover with baking paper for the last 10 minutes. Remove the stollen from the baking tray and let it cool down a little on a cake rack. Serve with butter