Cut 125 g butter into pieces. Knead butter, flour, salt, 1-2 cold water and 1 egg first with the dough hooks of the hand mixer, then with your hands to a smooth dough. Wrap the dough in foil and chill for about 30 minutes
Wash the chicken fillets, dab dry and season with salt. Heat oil in a pan. Fry the chicken fillets on each side for about 4 minutes until golden brown. Take them out, let them cool down and cut into cubes
Cut the chorizo into cubes. Peel garlic and chop finely. Wash spinach thoroughly and drain well. Heat 1 tablespoon of butter in a small pot. Add the spinach and garlic and let them collapse. Season with salt, pepper and nutmeg. Take out and chop coarsely
Roll out the short pastry on a floured work surface until round (approx. 28 cm Ø). Line a greased pie dish (cm 24 cm Ø) with the dough, press the edge firmly. Cut off protruding edges
Wash the tarragon, shake dry and cut the leaves into small pieces. Spread the spinach, meat and chorizo on top. Mix 3 eggs, milk and tarragon, season with salt and pepper. Pour egg milk over the tart
Bake the tart in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 30-35 minutes. Remove the tart and serve
Waiting time approx. 10 minutes