In a separate bowl, combine flour and baking powder.

In a large mixer bowl, mix the eggs, sugar, and vanilla on high speed until thoroughly combined.

In a small bowl mix together melted butter and vegetable oil.

Slowly pour the butter/oil mixture into the egg mixture on medium speed.

In a small bowl, mix together the half and half, milk, and lemon juice.

Then slowly add that mixture to large mixing bowl at medium speed.

Add dry ingredients and mix by hand, but do not over mix.

Gently fold in the chocolate chips and walnuts.

Spoon batter into well greased muffin tins, filling them to the top.

Sprinkle a little bit of granulated sugar on top of each muffin.

Bake in preheated 400 degree oven for 20 to 25 minutes or until a wooden toothpick inserted into the center of the muffin comes out clean.