In a heavy saucepan, melt the butter, oil, sugar, and salt.

Be careful when the mixture starts to boil that it does not burn. Let it caramelize, but don't let it get too dark. Remember that even after you take it off the heat, it will continue to cook. The picture below shows the approximate color, after cooking. I did not want to take a picture while it was cooking because I thought it might be a little dangerous.

Have ready a metal or heatproof bowl in a stand mixer.

Put the flour into the bowl, and carefully pour the butter mixture over the flour.

This is where you have to get a little creative. Add as much milk as necessary to make a ball, or add more flour if needed

Using the paddle attachment, mix the dough together until it forms a nice ball.

By using a stand mixer, the dough should be cool enough to handle.

Have ready a tart mold with a removable bottom.

While the oven is heating up, use the heel of your hand to move the dough all the way and up on the edges. Use a fork to reinforce the dough on the sides.

Prick the dough with a fork at least 10 times all over the bottom of the crust. There is no need for blind baking.

Bake the tart shell in the oven for about 15 minutes, or until the crust is golden brown.