Pulse a few times into a fine flour mix. Then add the warm milk and pulse again until a smooth and rather sticky dough comes together.
Then put the dough onto a clean and floured surface and knead it a few minutes. Wrap it in cling film and let the dough rest for about 10 minutes. Roll the dough out and coat a tart tin with it. Then prick the bottom with a fork.
Add the beaten eggs, the cream and the rum (optional).
Remove the bowl from the pan of boiling water. Beat the chocolate batter well. Gently pour the chocolate filling in the pre-baked tart shell.