Preheat oven to 400*. Have a cast iron muffin pan, place in the oven with each muffin hole with 1/2 teaspoon of butter. Place in oven to heat the cast iron pan and brown the butter. Or move your roast to one side of the roasting pan and pour off all but 4 TBS. of excess fat. (If you don't have enough dripping fat at the bottom of the roasting pan add the 4 Tblsp. of butter and heat the roasting pan in the 400* oven.
Place the flour, beaten eggs, milk and salt in a chilled bowl. Beat with an electric mixture or whisk by hand for about 2 minutes till it has a froth on top of the dough. Chill the dough in the refrig. for 1 hour. (Sometimes I just sip this step and it doesn't seem to matter). Lightly beat the pudding again.
Pour the chilled dough into each muffin hole or pour into the roasting pan that contain the juice of the roasts and the melted butter.