Reduce the heat to medium-low and stir in the flour. Cook the flour for 1 minute stirring constantly.
Gradually whisk in the milk and cream. Bring the sauce to a simmer for about 10 minutes
Gradually add the cheese stirring to blend.
Meanwhile cook the penne in a pot of salted boiling water for about 8 minutes. Add the peas and continue boiling until the pasta is tender but still very firm to the bite and the peas are bright green, about 1 minute. Drain pasta and peas.
Stir the bacon into the cheese sauce.
Stir the pasta and peas into the cheese sauce. The sauce will look loose but will continue to thicken once the pasta is added. If it thickens too much, add a little more milk or cream to thin it. Season with salt and pepper.
Pour into a 2½ quart casserole dish that has been greased.
Sprinkle the parsley over the pasta mixture then stir some of it into the mixture.
Preheat the broiler. In a small mixing bowl toss the breadcrumbs with the melted butter to coat well. Season with salt and sprinkle the breadcrumbs evenly over the pasta.
Broil until the topping is gold brown watching closely about 2 minutes
Let stand at room temperature for 5 minutes before serving.
Recipe by Sugar n' Spice Gals at https://sugar-n-spicegals.com/curtis-stones-gourmet-mac-n-cheese/