Cheesecake: Preheat oven to 325 degrees. In a stand mixer with the paddle attachment, blend cream cheese, sugar, salt, and extract until smooth. Add eggs, one at a time. Add sour cream and mix on low until blended. Pour heavy cream and Irish cream together, and slowly add to the cream cheese mixture while mixing on low. If desired, divide batter into three bowls and add different amounts of green food coloring to two before pouring all three into the prepared crust. Swirl gently with a knife to create a marbling effect. Wrap the springform pan in heavy duty foil, leaving the top open. Place in a large baking dish and add water until it reaches halfway up the pan. Bake on the middle rack until top is set, about one hour. Turn oven off and leave cheesecake in another 45 minutes. Chill overnight before slicing. Sauce: In a large pot, melt sugar over medium heat. Cook the liquefied sugar to a dark copper color. Add all butter at once and combine before turning off stove. Slowly whisk in heavy cream and ale until sauce is smooth. Use it right away or keep refrigerated for up to two weeks.