MAKE THE BISCUITS:Preheat the oven to 450 F.Cut shortening into flour, sugar, baking powder, and salt. Stir in milk.Turn dough onto lightly floured surface; knead 10 times. Roll ½” thick and cut out using a cookie cutter (I use the large lids from ball canning jars).Put on ungreased cookie sheet and bake 10-12 minutes or until just a hint of light brown.
MAKE THE CREAMED CHICKEN:While the biscuits are baking, melt butter over medium heat. Add flour, pepper, and ground mustard and use whisk to cook for 1-2 minutes over medium heat until it smells nutty and there is just a hint of it turning light brown.Slowly add milk, stirring constantly until it thickens, 4-5 minutes.Add chicken, peas, and drained pimientos and cook over medium heat until peas are softened and chicken hot - about 10 minutes.Add cheese; once melted it is ready to serve over biscuits.