Why don't you use code behind for this?
Label1.Text = "Generate " + Session["mType"].ToString() + " Template";
Anyway try like this & customize it
<asp:label id="Label1" runat="server" text="<%= Session[" mtype="].ToString() %>" font-bold="true" xmlns:asp="#unknown" />
And use
String.Format
or
Stringbuilder
for string concatenations