Rinse the tomatoes, dab them, cut the tops into small pieces, scoop out the insides, drain a little bit. Mash the blue cheese, add to the heated milk, stir until the cheese is dissolved.
Mix maizena (cornstarch) water, bind the cheese milk with it, cool a little bit. Whisk 2 egg yolks, fold in. Whip 2 egg whites until very stiff and fold into the cheese-milk mixture, season with salt and pepper and fold in the chopped tarragon leaves.
Fill the tomatoes with the mixture, place the lids on top, place in a greased ovenproof dish and bake in a heated oven at 225 degrees for about 15 minutes.
Note: The tomatoes must not touch each other in the mold, otherwise they will fall together.